U.S. patent application number 12/499131 was filed with the patent office on 2010-02-25 for noninvasive transdermal systems for detecting an analyte in a biological fluid and methods.
Invention is credited to Jack L Aronowitz, Joel R. Mitchen, John Weiss, Irwin Weitman.
Application Number | 20100049016 12/499131 |
Document ID | / |
Family ID | 23014190 |
Filed Date | 2010-02-25 |
United States Patent
Application |
20100049016 |
Kind Code |
A1 |
Aronowitz; Jack L ; et
al. |
February 25, 2010 |
Noninvasive Transdermal Systems for Detecting an Analyte in a
Biological Fluid and Methods
Abstract
The present invention relates to noninvasive transdermal systems
comprised of a noninvasive transdermal patch and a reflectometer.
The noninvasive transdermal patches are comprised of a wet
chemistry component and a dry chemistry component. The wet
chemistry component is a liquid transfer medium in the form of a
gel layer for the extraction and liquid bridge transfer of the
analyte of interest from the biological fluid within or beneath the
skin to the dry chemistry component. The dry chemistry component is
a reagent system for interacting with the analyte of interest
(glucose) to generate a color change. The reflectometers include a
modulated light source for emitting light to illuminate a target
surface which possesses a certain color and shade of color for
detection by an optical detector. The output signal is processed
for determining a corresponding quantity of quality
measurement.
Inventors: |
Aronowitz; Jack L; (Delray
Beach, FL) ; Mitchen; Joel R.; (Pompano Beach,
FL) ; Weiss; John; (Holtsville, NY) ; Weitman;
Irwin; (East Northport, NY) |
Correspondence
Address: |
SALIWANCHIK LLOYD & SALIWANCHIK;A PROFESSIONAL ASSOCIATION
PO Box 142950
GAINESVILLE
FL
32614
US
|
Family ID: |
23014190 |
Appl. No.: |
12/499131 |
Filed: |
July 8, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09266346 |
Mar 11, 1999 |
7577469 |
|
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12499131 |
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Current U.S.
Class: |
600/310 |
Current CPC
Class: |
G01N 21/8483 20130101;
A61B 5/14532 20130101; A61B 5/1455 20130101 |
Class at
Publication: |
600/310 |
International
Class: |
A61B 5/00 20060101
A61B005/00 |
Claims
1. A noninvasive transdermal system for detecting an analyte in
interstitial fluid extracted from or underneath the skin of a
subject, said noninvasive transdermal system comprising: (a) a
noninvasive transdermal patch comprising a target surface having a
dry chemistry component for interacting with the analyte to
generate color or shade of color at said target surface, said dry
chemistry component having a sensitivity which enables it to detect
the analyte extracted from interstitial fluid, and a wet chemistry
component for transferring the analyte from the interstitial fluid
in or underneath the skin to said dry chemistry component in an
amount sufficient so that said dry chemistry component can detect
the analyte; and (b) a reflectometer comprising a modulated light
source for emitting light to illuminate said target surface which
possesses a certain color and shade of color following interaction
with the analyte; an optical detector for detecting light that is
reflected from said target surface and generating a first output
indicative of detected light; means for processing the first output
to generate a feedback signal for application to the optical
detector to compensate for any shift in the first output resulting
from the detection of ambient light by the optical detector, and
differentially amplify the first output to generate a second
output; and a detector for synchronously demodulating the second
output to generate a substantially steady DC output voltage that is
indicative of the color or shade of color at said target
surface.
2. A noninvasive transdermal system for detecting an analyte in a
biological fluid extracted from or underneath the skin of a
subject, said noninvasive transdermal system comprising: (a) a
noninvasive transdermal patch comprising a target surface having a
dry chemistry component for interacting with the analyte to
generate color or shade of color at said target surface, a dry
chemistry component for interacting with the analyte to detect the
analyte, said dry chemistry component having a sensitivity which
enables it to detect the analyte extracted from interstitial fluid,
and a wet chemistry component for transferring in about 15 minutes
or less the analyte from the interstitial fluid in or underneath
the skin to said dry chemistry component in an amount sufficient,
so that said dry chemistry component can interact with the analyte
to generate color or shade of color at said target surface for
detecting the analyte, said wet chemistry component consisting
essentially of a gel and a skin permeate enhancer; (b) a
reflectometer comprising a light source for emitting light to
illuminate said target surface which possesses a certain color and
shade of color; an optical detector circuit for detecting light
that is reflected from the target surface and generating a
substantially steady DC output voltage that is indicative of the
color or shade of color at said target surface; a stored look-up
table or mathematical formula correlating steady DC voltage values
to corresponding quantity or quality measurements for each one of a
plurality of different tests; and a processor for consulting the
stored look-up table or mathematical formula for a certain test
being performed, and converting the steady DC voltage indicative of
the color or shade of color at said target surface into a
corresponding quantity or quality measurement in accordance with
that certain test.
3. A noninvasive transdermal system for detecting an analyte in a
biological fluid extracted from or underneath the skin of a
subject, said noninvasive transdermal system comprising: (a) a
noninvasive transdermal patch comprising a target surface having a
dry chemistry component for interacting with the analyte to
generate color or shade of color at said target surface, a dry
chemistry component for interacting with the analyte to detect the
analyte, said dry chemistry component having a sensitivity which
enables it to detect the analyte extracted from interstitial fluid,
and a wet chemistry component for transferring in about 10 minutes
or less the analyte from the interstitial fluid in or underneath
the skin to said dry chemistry component in an amount sufficient,
so that said dry chemistry component can interact with the analyte
to generate color or shade of color at said target surface for
detecting the analyte, said wet chemistry component consisting
essentially of a gel and a skin permeate enhancer; (b) a
reflectometer comprising a light source for emitting light to
illuminate said target surface which possesses a certain color and
shade of color; an optical detector circuit for detecting light
that is reflected from said target surface and generating a
substantially steady DC output voltage that is indicative of the
color or shade of color at said target surface; a stored look-up
table or mathematical formula correlating steady DC voltage values
to corresponding quantity or quality measurements for each one of a
plurality of different tests; means for calibrating the
reflectometer to determine an offset for application to read DC
output voltages corresponding to a certain color or shade of color;
and a processor for the determined offset to adjust the steady DC
voltage indicative of the color or shade of color at said target
surface and consulting the stored look-up table or mathematical
formula and converting the adjusted steady DC voltage into a
corresponding quantity or quality measurement for the analyte.
Description
FIELD OF THE INVENTION
[0001] The present invention concerns noninvasive transdermal
systems and methods for analyte extraction from a biological fluid
within or beneath the skin, such as interstitial fluid, and
detection of the analyte. More particularly, the present invention
relates to noninvasive transdermal systems comprised of a
noninvasive patch and a reflectometer for detecting an analyte of
interest and methods. The noninvasive patches include a wet
chemistry component for extraction of the analyte of interest from
a biological fluid within or beneath the skin and presentation to a
dry chemistry component which interacts with the analyte for
indicator molecule formation to confirm detection of the analyte,
and methods of use thereof.
[0002] The present invention also relates to reflectometer
technology and, in particular, to a method and apparatus for
detecting and measuring color shades with a relatively high degree
of accuracy. Where the color shades are indicative of a certain
measurable quantity or quality, the present invention further
relates to method and apparatus for converting the detected color
shade into a corresponding quantity or quality measurement.
BACKGROUND
[0003] The determination of an individual's physiological status is
frequently assisted by chemical analysis for the existence and/or
concentration level of an analyte in a body fluid. This practice is
common in the diagnosis of diabetes and in the management of this
disease. Blood sugar levels can generally fluctuate with the time
of day and with the period since the individual's last consumption
of food. Management of diabetes often, thus, requires the frequent
sampling and analysis of the diabetic's blood for determination of
its relative glucose level. The management of this disease by the
diabetic will typically involve the sampling of his/her own blood,
the self-analysis of the sample for its relative glucose content
and the administration of insulin, or the ingestion of sugar,
depending upon the indicated glucose level.
[0004] Presently, the only approved method for home monitoring of
blood chemistry requires drawing blood by using a lance, usually by
sticking a finger, and placing a drop of blood on a chemical strip.
The resulting chemical reaction causes a change in the color of the
strip with that change being read by a desk-top reflectance meter
to provide an indication of blood sugar level. Another method also
requires drawing blood, placing a drop of blood on a disposable
printed circuit (PC) board, and measuring the electrical response
of the blood to detect blood sugar level. Some attempts to use
infrared techniques to look through the skin to make blood sugar
determinations have proven to be less reliable and too expensive
for commercial application.
[0005] Diabetics who need to control their insulin level via diet
or insulin injection may test themselves several times per day,
i.e., five or six times per day, the frequency recommended by the
American Diabetes Association. Some may choose to test less often
than recommended to avoid the unpleasantness associated with
drawing blood. Unfortunately, the current methods of monitoring
blood glucose levels has many drawbacks. The current methods
generally rely upon finger lancing to monitor blood glucose levels,
which is not easy for anyone, especially young children and the
elderly. Moreover, because blood is involved, there is always the
risk of infection and of transmission of blood borne diseases, such
as AIDS. Still further, special procedures and systems for handling
and disposing of the blood are required. If the blood glucose
concentrations in such individuals are not properly maintained, the
individuals become susceptible to numerous physiological problems,
such as blindness, circulatory disorders, coronary artery disease,
and renal failure. For these reasons, there is a great unmet need
for a noninvasive method for monitoring blood glucose levels. A
substantial improvement in the quality of life of persons suffering
from various maladies, such as diabetes mellitus, could be attained
if the concentrations of species in body fluids are noninvasively
determined. There is accordingly a considerable amount of interest
in the development of procedures for making blood sugar level
determinations that avoid any need for inflicting injury to the
patient.
[0006] There are a number of devices on the market to assist the
diabetic in the self-testing of the blood sugar level. One such
device, developed by Audiobionics (now Garid, Inc.) and described
in U.S. Pat. No. 4,627,445, issued Dec. 9, 1986, involves the use
of a fixture containing a multi-layered element for the collection
of the whole blood sample, the transport of the sample from the
point of application on the element to a porous membrane, and the
analysis of the blood sample for its glucose contents by a dry
chemistry reagent system which is present within the porous
membrane.
[0007] Other such devices described in U.S. Pat. Nos. 5,462,064 and
5,443,080 and issued to J. P. D'Angelo et al. involve the use of a
multi-part system to collect and analyze constituents of body
fluid. In D'Angelo et al., the systems rely upon, among other
things, a multilayered gel matrix which includes a separate
activation gel layer and a separate collection gel layer disposed
below the activation gel layer, an osmotic flow enhancer, such as
ethyl ether, to facilitate the collection of an analyte fluid, and
a chemistry detection methodology to aid in the visual or
electronic determination of an analyte under investigation. Ethyl
ether, however, is a known skin irritant which is flammable and
explosive.
[0008] Another such device described in U.S. Pat. No. 5,203,327 and
issued to D. W. Schoendorfer et al., involves a method and
apparatus for the non-invasive determination of one or more
preselected analytes in perspiration. In D. W. Schoendorfer, et
al., the fluid is collected in a dermal concentration patch and
concentrated by driving off a portion of the substantial water
fraction under the influence of body heat, and the analyte is
optimally complexed with an immobilized specific binding partner
and an indicium of the presence of the analyte is usually
experienced.
[0009] Other such devices are described in U.S. Pat. Nos.
4,960,467; 4,909,256; 4,821,733; 4,819,645; and 4,706,676 and
issued to Peck. According to these patents, the Peck devices
involve a dermal substance collection device (DSCD) which provides
for the non-invasive, instantaneous and continuous monitoring of
chemical substances which are present in detectable amounts in
either or both interstitial fluid or sweat or which are on or in
the skin. More particularly, the Peck transdermal substance
collection devices are comprised of three essential components: (1)
a substance binding reservoir, wettable by (2) a liquid transfer
medium which allows for liquid bridge transfer of a soluble
substance from the skin surface to the biding reservoir by virtue
of its wettability by the liquid, and (3) an occlusive cover.
[0010] Exemplary of other systems have been previously proposed to
monitor glucose in blood, as is necessary, for example, to control
diabetic patients. This is represented, for example, by Kaiser,
U.S. Pat. No. 4,169,676, Muller, U.S. Pat. No. 4,427,889, and Dahne
et al., European Patent Publication No. 0 160 768, and Bauer et
al., Analytica Chimica Acta 197 (1987) pp. 295-301.
[0011] In Kaiser, glucose in blood is determined by irradiating a
sample of the blood with a carbon dioxide laser source emitting a
coherent beam, at a single frequency, in the mid-infrared region.
An infrared beam derived from the laser source is coupled to the
sample by way of an attenuated total reflectance crystal for the
purpose of contacting the blood sample. The apparatus uses double
beam instrumentation to examine the difference in absorption at the
single frequency in the presence and absence of a sample.
[0012] Muller discloses a system for quantifying glucose in blood
by irradiating a sample of the blood with energy in a single beam
from a laser operating at two frequencies in the mid-infrared
region. The infrared radiation is either transmitted directly to
the sample or by way of an attenuated total reflectance crystal for
in vitro sampling. One frequency that irradiates the sample is in
the 10.53-10.6 micrometer range, while the other irradiating
frequency is in the 9.13-9.17 micrometer range. The radiation at
the first frequency establishes a baseline absorption by the
sample, while glucose absorption by the sample is determined from
the intensity reduction caused by the sample at the second
wavelength. The absorption ratio by the sample at the first and
second frequencies quantifies the glucose of the sample.
[0013] Dahne et al. employ near-infrared spectroscopy for
non-invasively transmitting optical energy in the near infrared
spectrum through a finger or earlobe of a subject. Also discussed
is the use of near-infrared energy diffusely reflected from deep
within the tissue. Responses are derived at two different
wavelengths to quantify glucose in the subject. One of the
wavelengths is used to determine background absorption, while the
other wavelength is used to determine glucose absorption. The ratio
of the derived intensity at the two different wavelengths
determines the quantity of glucose in the analyte biological fluid
sample.
[0014] Bauer et al. disclose monitoring glucose through the use of
Fourier-transform infrared spectrometry wherein several absorbance
versus wavelength curves are illustrated. A glucose concentration
versus absorbance calibration curve, is constructed from several
samples having known concentrations, in response to the intensity
of the infrared energy absorbed by the samples at one wavelength,
indicated as preferably 1035 cm.sup.-1.
[0015] Notwithstanding the above, the most frequently employed
systems for determining the concentration of molecular substances
in biological fluids have used enzymatic, chemical and/or
immunological methods. However, these techniques generally require
invasive methods to draw a blood sample from a subject; typically,
blood must be drawn several times a day by a finger prick, such as
presently employed by a diabetic and externally determining the
glucose level, generally by chemical reaction followed by
colorimetric comparative testing. For example, in the determination
of glucose by diabetics, such invasive techniques must be performed
using present technology.
[0016] Because the prior art invasive techniques are painful,
individuals frequently avoid having blood glucose measured. For
diabetics, the failure to measure blood glucose on a prescribed
basis can be very dangerous. Also, the invasive techniques, which
rely upon lancing blood vessels, create an enhanced risk for
disease transmission and infection.
[0017] Thus, there remains a need in many diverse applications for
a system for the noninvasive, painless determination of a
preselected analyte in a body fluid, such as interstitial fluid,
which can be utilized to detect the presence of the preselected
analyte. Clearly, in the case of diabetics, it would be highly
desirable to provide a less invasive system for analyzing glucose
concentrations in the control of diabetes mellitus. However, with
respect to transdermal detection mechanism, the extracted analytes
which are indicative of widely varying blood sugar levels may
produce only very slight changes in developed color shade. In many
instances, the difference between developed color shade for an
acceptable and an unacceptable blood sugar level cannot be
accurately and repeatably detected by the naked eye. To obtain the
non-invasive benefits of transdermal glucose measurement technology
while ensuring measurement accuracy in what may comprise a life
critical testing procedure, it is therefore imperative that the
fallible human activity of color shade evaluation and comparison be
eliminated from the testing and measurement process.
[0018] There is accordingly a need for an ultra-sensitive meter
capable of accurately resolving the full range of developed subtle
color shade changes produced as a result of transdermal patch
extraction and processing of certain analytes of interest.
Preferably, the meter should be small, lightweight and portable
(hand held). Beyond the obvious requirements for improved
sensitivity to subtle differences in color shade, this meter should
account for the effects of portability which are adverse to reading
accuracy such as background light changes, temperature changes, and
unsteady hand-held operation (for example, due to device pressure
variation, rotation, and movement), and which are not normally
associated with the desk-top meters that are widely employed for
measuring blood sugar levels on test strips. Moreover, the entire
system for noninvasive detection should be low-cost and suitable
for convenient use by non-medical personnel.
SUMMARY OF THE INVENTION
[0019] In brief, the present invention overcomes certain of the
above-mentioned drawbacks and shortcomings through the discovery of
a novel transdermal system for detecting an analyte of interest in
a biological fluid and methods concerning same, without resort to
prior standard invasive, painful techniques. In accordance with the
present invention, the novel noninvasive transdermal systems
provide for sample collection and detection in the form of a
simple, easy-to-use, integrated system which is low-cost and
suitable for convenient use by non-medical personnel. Moreover,
because the novel transdermal systems of the present invention are
noninvasive and painless, as compared to the invasive techniques
generally utilized heretofore, e.g, a finger prick or finger lance,
individual compliance should be enhanced, and the risk of disease
transmission and infection should be reduced.
[0020] With the foregoing in mind and other objects in view, there
is provided, in accordance with the present invention, a
noninvasive transdermal system for collecting and detecting an
analyte of interest in a biological fluid within or underneath the
skin. Generally speaking, the noninvasive transdermal systems of
this invention are comprised of two essential components: (1) a dry
chemistry component; and (2) a wet chemistry component. The dry
chemistry component comprises a super sensitive or conditioned
membrane containing a compliment of chemical reagents which are
specific for reacting with one or more analytes of interest. The
interaction of the analyte(s) and such chemical reagents is
manifest by the release or formation of indicator molecules, e.g.,
color change, which is indicative of the presence of the analyte(s)
in the biological fluid. The surface of the super sensitive or
conditioned membrane, which is receptive of and exposed to the
analyte of interest, is relatively dense, thereby being generally
free of cells, particles and/or other micromolecules which can
potentially interfere with reaction of the analyte and the chemical
reagents and/or the detection of a reporter molecule. In contrast,
the opposing surface of the super sensitive or conditioned membrane
is substantially less dense (more porous), thereby allowing for
infusion of the reagent system during manufacture, and the
formation, diffusion and visualization of reporter or indicator
molecules, which are indicative of the presence of the analyte of
interest and its level of concentration in the body fluid. The
super sensitive or conditioned membranes of the present invention
have the unique ability to detect analytes in very small sample
volumes, e.g., about 25 mcl, in very small concentrations which are
at least as low as about 5 mg/dl or about 5 mcg/ml.
[0021] The wet chemistry component of the present invention
comprises a generally liquid transfer medium which allows for
liquid bridge transfer or extraction of an analyte of interest from
the biological fluid within or underneath the skin to the super
sensitive or conditioned membrane for reaction with the reagents to
release or form the reporter or indicator molecule, which is
indicative of the presence of the analyte in the biological
fluid.
[0022] More specifically, and in accordance with the present
invention, the compliment of reagents, with which the membrane is
conditioned, includes a chemical reactant and a color developer
specifically provided for an analyte of interest. Also in
accordance with the present invention, the liquid transfer medium
is in the form of a gel layer or gel matrix which permits for
liquid transfer or extraction of the soluble analyte under
investigation from the biological fluid within or underneath the
skin to the site of reaction at the super sensitive or conditioned
membrane. Preferably, the gel layer is a hydrophobic gel which is
inert, nonflammable and nonirritating to the skin. An especially
preferred hydrophobic gel in accordance with the present invention
is a gel formulated with carboxy polymethylene, marketed or sold
under the brand name Carbopol.RTM., and deionized water (18 meg
ohm) in a concentration of from about 0.5% to about 2.0%, and
preferably in a concentration of about 1%.
[0023] In accordance with a further feature of the present
invention, the gel includes a permeation skin enhancer selected for
the analyte to be detected for enhancing the liquid bridge transfer
or extraction of the analyte from the biological fluid within or
underneath the skin to the super sensitive or conditioned membrane
for reaction and detection. Preferred skin permeation enhancers
contemplated by the present invention are those which are
nonflammable, nonexplosive and nonirritating to the skin, and which
do not interfere with the analyte under investigation, its transfer
to the super sensitive or conditioned membrane and its interaction
with the chemical reagents. In accordance with the present
invention, a preferred skin permeation enhancer is propylene glycol
elegantly admixed in the gel in a concentration of from about 5% to
about 20%, and especially admixed in the gel in a concentration of
about 10%. Thus, an especially preferred gel in accordance with the
present invention comprises about 1% carboxy polymethylene, e.g.,
Carbopol.RTM., and about 10% propylene glycol in deionized water
(18 meg ohm).
[0024] Alternatively, and also in accordance with the present
invention, a skin permeation enhancer may be first directly applied
to the targeted skin area to which the transfer medium or gel is
applied. While the present invention contemplates the use of a
permeation enhancer separate from or in addition to the transfer
medium gel, it has been surprisingly discovered that, when a skin
permeation enhancer is incorporated into the transfer medium or
gel, it is not necessary to apply a skin permeation enhancer
directly to the skin before applying the novel noninvasive
transdermal systems of the present invention.
[0025] Also in accordance with the present invention, the novel
noninvasive transdermal systems can be configured as a component of
a noninvasive transdermal patch for collection and detection of an
analyte in a biological fluid within or underneath the skin. When
configured into a noninvasive transdermal patch, it is contemplated
that the dry chemistry component and the wet chemistry component
are maintained separately prior to use and that, upon use, the
super conditioned membrane and the transfer medium shall be the
exclusive means of access of the analyte under investigation to the
chemical reagents infused onto and/or within the membrane.
[0026] In a preferred embodiment in accordance with the present
invention, the body fluid from which an analyte may be
transdermally extracted is interstitial fluid.
[0027] In yet a further feature of the present invention, an
electronic interpretation component may be utilized for detecting
the reporter or indicator molecules, e.g., color change, generated
from the presence of the analyte in the biological fluid and its
reaction with the chemical reagents. The electronic interpretation
components should include a light source for illuminating the
indicator molecule, a photosensor sensing a reflecting intensity
from the indicator molecules and a system for interpreting the
measured reflectance intensity and providing information regarding
a result of the interpretations. Thus, the present invention
comprises a reflectometer for detecting and measuring subtle
changes in color and shade of color. In general, a pulsating light
source illuminates a target surface which possesses a certain color
and shade of color. An optical detection circuit synchronously
detects light that is reflected from the target surface and
generates an output signal whose voltage is indicative of the color
and shade of the target surface. This voltage is then processed to
make an evaluation and identification of any measurable quantity or
quality that is represented by the detected color or shade of
color.
[0028] More specifically, a modulated light source emits light to
illuminate the colored target surface, where the specific color or
shade of color is indicative of a certain measurable quantity or
quality (such as an analyte concentration). The modulated light
that is reflected from the target surface is detected by an optical
detector. The output signal from the optical detector is
differentially amplified to produce an AC output signal indicative
of the color and shade of the target surface. The output signal
from the optical detector is further processed and fed back to the
optical detector to compensate for any shift in the DC level of the
AC output signal caused by the detection of ambient light or the
influence of other external factors. The output signal from the
differential amplifier is then demodulated by a synchronous
detector to produce a substantially steady DC voltage that is
indicative of the color or shade of color at the target surface.
This DC voltage is converted to a corresponding digital value, and
that digital value is converted using a look-up table or other
mathematical formula into a corresponding quantity or quality
measurement.
[0029] It should nevertheless be understood that, while any
commercial reflectometer capable of reading a color change in a
wavelength range of, for example, about 500 nm to about 930 nm at
an angle of reflection in the range of about 30.degree. to about
90.degree. with a voltage of from about 200 mV to about 1 mV with a
sensitivity of about .+-.0.1 mV, may be used in accordance with the
novel noninvasive transdermal systems of the present invention, the
reading head of such reflectometers should preferably be configured
so as to interface precisely with the recess or through aperture
leading to the dry chemistry component of the novel noninvasive
transdermal systems. Preferably, the reading head of a
reflectometer should have a matching sensor and LED which can read
reflectance from color in a wavelength range of from about 650 nm
to about 670 nm at an angle of reflectance in the range of about
35.degree. to about 45.degree. with such sensitivity. FIG. 9
depicts an exemplary reflectometer in accordance with the present
invention having a reading head which is configured for precise
interface with a recess or through aperture that leads to the dry
chemistry component or membrane. The reflectometer depicted in FIG.
9 further includes a visual display for communicating the results
detected by the reflectometer. FIG. 10 illustrates a cross section
of a reflectometer depicted in FIG. 9 for interfacing with a
transdermal patch of the present invention at about a
40.degree.-45.degree. angle of reflectance for reading color
intensity for analyte detection.
[0030] With the above-listed objects in view, there is provided, in
accordance with the present invention, a collection and indication
apparatus for biological fluid constituent analysis, which
comprises a collector component for noninvasively and transdermally
collecting a body fluid analyte from an individual or subject in
the form of a dry chemistry component including a compliment of
chemical reagents for reacting with the analyte for indicating its
presence and a wet chemistry component for extracting and
transferring the analyte from the body fluid within or underneath
the skin to the chemical reagents; and a configuration specifically
designed for keeping the dry chemistry component and the wet
chemistry component intact and separate from one another during
non-use, but which allows them to intimately engage one another
during testing, so that the dry chemistry component is continuously
and uniformly wetted during testing by the wet chemistry component
and the analyte under investigation can be extracted and
transferred from the biological fluid within or underneath the skin
to the super sensitive or concentrated membrane for interaction
with the chemical reagents to generate the reporter or indicator
molecules, e.g., color change, to confirm analyte presence.
Preferably, the body fluid is interstitial fluid from which the
analyte is transdermally and noninvasively extracted and
collected.
[0031] In other words, the novel noninvasive, transdermal systems
of the present invention include three major operational
components. The first is the wet chemistry component which
functions as the liquid bridge for transferring the analyte of
interest from the biological fluid within or underneath the skin to
the dry chemistry component, the second component is the dry
chemistry component infused with a chemical reaction system
specifically for interacting with the analyte of interest to detect
its presence, and the third component is a support or housing for
the systems which are configured to ensure that the wet and dry
chemistry components remain separate during nonuse, but are in
direct and continuous contact when the systems are in use and which
enables the individual users to physically hold the systems and
review the generated data in a rapid and meaningful way. In
addition, the novel noninvasive transdermal systems of the present
invention contemplate the use of a permeation skin enhancer admixed
into the wet chemistry component and/or at the targeted skin areas
prior to application of the novel noninvasive transdermal systems
to such skin areas. Still further, the novel noninvasive
transdermal systems of the present invention contemplate an
electronic interpretation component especially configured for
precise interfacing with the dry chemistry component, so that the
reading head can read changes in color intensity in a preferred
wavelength range of about 650 nm.+-.10 nm at an angle of
reflectance of about 40.degree. with a sensitivity precision of
about .+-.0.1 mV. In other words, the electronic interpretation
component of the system is configured so as to read the patch
component in the event of a visual impairment, or if a more precise
numerical value is required, it will give a report in that
format.
[0032] A novel method of combining test chemistries known to those
in the healing arts with the interstitial fluid collection medium
in such a manner as to cause to be noninvasively and transdermally
extracted from or through the skin, a quantity of analyte of
interest sufficient for the chemical test to proceed and then to
have the ability to read and record the results in a very short
period of time, e.g., a few minutes, is described. This is one of
the major objects of this invention.
[0033] In a preferred embodiment, the present invention
contemplates small disposable transdermal patches for use with a
reflectometer to detect an analyte such as glucose. In accordance
with the present invention, the small disposable transdermal
patches measure blood glucose levels noninvasively. In actuality,
the small disposable transdermal patches of the present invention
have the unique ability to detect the levels of glucose in
interstitial fluid which directly correlate to those levels in the
blood. Briefly, and not to be limited, the process is believed to
occur as follows. A small disposable transdermal patch of the
present invention, which is strategically placed on the targeted
skin area, painlessly draws glucose from the interstitial fluid
through the skin. The glucose is transported by the skin permeation
enhancer combined with a gel capable of transporting glucose
through the stratum corneum (upper level of the epidermis). The
glucose in the interstitial fluid then undergoes a glucose-specific
biochemical reaction at the site of the dry chemistry membrane, the
biochemical reaction of which are contained within the dry
chemistry membrane in the patch. This biochemical reaction results
in a color formation which is then measured by a reflectometer and
directly correlated to the blood glucose levels. It is believed
that the membrane based technology of the present invention is at
least 100, if not 400-500, times more sensitive for detection of
very small concentrations of an analyte, e.g., about 5 mg/dl or 5
mcg/ml, in a very small volume of fluid, e.g., about 25 mcl, than
what is being currently used with finger stick or finger lancing
technology. Thus, and in accordance with the present invention, the
extraction and detection process only requires a small patch and a
small hand held reflectometer. And, because blood is not at all
involved, pain and the risk of infection and disease transmission
generally associated with glucose monitoring have been eliminated.
Moreover, special handling procedures or disposal systems are no
longer required.
[0034] The noninvasive transdermal systems of the present invention
analyze analytes in interstitial fluid rather than blood.
Interstitial fluid is the nutrient fluid between the cells within
the body tissues. The volume of interstitial fluid in the body is
more than three time the blood volumes, and the concentrations of
various constituents of the interstitial fluid are generally in
equilibrium with the concentrations of those same constituents in
blood. In accordance with the present invention, it is believed
that small quantities of analyte in the interstitial fluid diffuse
into the novel noninvasive transdermal systems with the aid of the
gel in combination with a skin permeation enhancer. Once inside the
systems of the present invention, the analyte of interest, e.g.,
glucos, from the interstitial fluid undergoes an enzymatic reaction
which leads to the formation of colored indicator material. The
color produced is believed to be proportional to the concentration
of the analyte in the interstitial fluid, which in turn is
proportional to the analyte concentration in the blood. This color
is measured by, for example, surface reflectance via a
fixed-wavelength optical meter, and is then compared to onboard
calibration values. The result for the detected analyte is
typically displayed in units of mg/dl.
[0035] An integral component of the invention is the transdermal
patch which allows the system to work as a non-invasive skin test
for clinical analytes. Additionally, what is shown and described
are various configurations, all of which work together as a new and
novel system to evaluate chemical analytes from noninvasively and
transdermally extracted biological fluids.
[0036] Other features which are considered as characteristic for
the invention are set forth in the appended claims.
[0037] Although the present invention is illustrated and described
herein as embodied in an integrated noninvasive and transdermal
system for biological fluid constituent analysis, it is
nevertheless not intended to be limited to the details shown, since
various modifications and structural changes may be made therein
without departing from the spirit of the invention and within the
scope and range of equivalents of the claims.
[0038] The construction of the invention, however, together with
additional objects and advantages thereof will be best understood
from the following description of specific embodiments when read in
connection with the accompanying FIGS. and examples.
[0039] The above features and advantages of the present invention
will be better understood with reference to the following detailed
description and examples. It should also be understood that the
particular methods and formulations illustrating the present
invention are exemplary only and not to be regarded as limitations
of the present invention.
BRIEF DESCRIPTION OF THE FIGS.
[0040] Reference is now made to the accompanying FIGS. in which a
more complete understanding of the systems, including the methods
and apparatus, of the present invention may be acquired by
reference to the following Detailed Description when taken in
conjunction with the accompanying FIGS., wherein:
[0041] FIG. 1A is a perspective view of a noninvasive transdermal
patch according to one embodiment of the present invention;
[0042] FIG. 1B is a cross-sectional view along the line 1A-1A of
the noninvasive transdermal patch of FIG. 1A;
[0043] FIG. 1C is a perspective of a noninvasive transdermal patch
illustrated in FIG. 1A but in a closed position;
[0044] FIG. 2 is an exploded elevational view of an alternative
noninvasive transdermal patch of FIG. 1A in accordance with the
present invention;
[0045] FIG. 3 is a perspective view of a noninvasive transdermal
patch according to yet another embodiment of the present
invention;
[0046] FIG. 4 is a perspective view of a noninvasive transdermal
patch according to another embodiment of the present invention;
[0047] FIG. 5 is an exploded elevational view of a noninvasive
transdermal patch according to yet another embodiment of the
present invention;
[0048] FIG. 6 is a perspective view of a noninvasive transdermal
patch according to another embodiment of the present invention;
[0049] FIG. 7 is an exploded elevational view of a noninvasive
transdermal patch according to yet another embodiment of the
present invention;
[0050] FIG. 8 is an exploded elevational view of a noninvasive
transdermal patch according to yet another embodiment of the
present invention;
[0051] FIG. 9 is a perspective view of a reflectometer in
accordance with the present invention;
[0052] FIG. 10 is a cross-sectional view of the reading head of the
reflectometer of FIG. 9;
[0053] FIG. 11 is a plot of data of an oral glucose tolerance test
comparing the results obtained from a noninvasive transdermal patch
of the present invention with the results obtained from capillary
blood glucose using the APG method;
[0054] FIG. 12 is a plot of data of an oral glucose tolerance test
comparing the results obtained from a noninvasive transdermal patch
of the present invention with the results obtained from capillary
blood glucose using the APG method;
[0055] FIG. 13 is a plot of data of the results of testing
linearity of glucose patch reaction chemistry in glucose patches of
the present invention when increasing concentrations of
glucose;
[0056] FIG. 14 is a graph of data depicting an actual calibration
curve for a noninvasive transdermal glucose patch of the present
invention;
[0057] FIG. 15A is a table depicting the data of the calibration
curve of FIG. 14;
[0058] FIG. 15B is a table of data corresponding to FIG. 11;
[0059] FIG. 16 illustrates plots of data which compares the results
obtained from a noninvasive transdermal patch of the present
invention with results obtained from capillary blood glucose
utilizing standard LSII methods;
[0060] FIG. 17 illustrates plots of data which compares the results
obtained from a noninvasive transdermal patch of the present
invention with results obtained from capillary blood glucose
utilizing standard LSII methods;
[0061] FIG. 18 illustrates plots of data which compares the results
of a noninvasive transdermal patch of the present invention with
the results obtained from capillary blood glucose utilizing
standard LSII methods;
[0062] FIG. 19 is a plot of data which shows the correlation of
results between a noninvasive transdermal patch of the present
invention with results obtained from capillary blood glucose
utilizing a standard method;
[0063] FIG. 20 is a plot of data which shows the correlation of
results obtained from a noninvasive transdermal patch of the
present invention with results obtained from capillary blood
glucose utilizing a standard method;
[0064] FIG. 21 is a bar graph of data which shows the results
obtained from noninvasive transdermal patches of the present
invention constructed with different gels which are tested with
different wipes;
[0065] FIG. 22 is a bar graph of data which shows the results
obtained from noninvasive transdermal patches of the present
invention constructed with different gels which are tested with
different wipes;
[0066] FIG. 23 is a bar graph of data which shows the results
obtained from noninvasive transdermal patches of the present
invention constructed with different gels which are tested with
different wipes;
[0067] FIG. 24 is a bar graph of data which shows the results
obtained from noninvasive transdermal patches of the present
invention constructed with different gels which are tested with
different wipes;
[0068] FIG. 25 is a bar graph of data which shows the results
obtained from noninvasive transdermal patches of the present
invention constructed with different gels which are tested with
different wipes;
[0069] FIG. 26 describes generally a method of testing the
permeation enhancing power of the skin permeation enhancer in
accordance with the present invention;
[0070] FIG. 27 is a plot of data which compares the results
obtained from a noninvasive transdermal patch of the present
invention with results obtained from capillary blood glucose
utilizing standard LSII methods;
[0071] FIG. 28 is a plot of data which compares the results
obtained from a noninvasive transdermal patch of the present
invention with results obtained from capillary blood glucose
utilizing standard LSII methods;
[0072] FIG. 29 is a plot of data showing the sensitivity of a
noninvasive transdermal glucose patch of the present invention;
[0073] FIG. 30 is a plot of data comparing results obtained from a
noninvasive transdermal patch of the present invention with results
obtained from blood glucose by standard method;
[0074] FIG. 31 is a plot of data comparing results obtained from a
noninvasive transdermal patch of the present invention with results
obtained from blood glucose by standard method;
[0075] FIG. 32 is a plot of data comparing results obtained from a
noninvasive transdermal patch of the present invention with results
obtained from blood glucose by standard method;
[0076] FIG. 33 is a plot of data comparing results obtained from a
noninvasive transdermal patch of the present invention with results
obtained from blood glucose by standard method;
[0077] FIG. 34 is a plot of data which compares the results
obtained from a noninvasive transdermal patch of the present
invention with results obtained from capillary blood glucose
utilizing standard method;
[0078] FIG. 35 is a plot of data which compares the results
obtained from a noninvasive transdermal patch of the present
invention with results obtained from capillary blood glucose
utilizing standard method;
[0079] FIG. 36 is a plot of data which compares the results
obtained from a noninvasive transdermal patch of the present
invention with results obtained from capillary blood glucose
utilizing standard method;
[0080] FIG. 37 is a plot of data which compares the results
obtained from a noninvasive transdermal patch of the present
invention with results obtained from capillary blood glucose
utilizing standard method;
[0081] FIG. 38 is a plot of data which compares the results
obtained from a noninvasive transdermal patch of the present
invention with results obtained from capillary blood glucose
utilizing standard method;
[0082] FIG. 39 is a plot of data which compares the results
obtained from a noninvasive transdermal patch of the present
invention with results obtained from capillary blood glucose
utilizing standard method;
[0083] FIG. 40 is a plot of data which compares the results
obtained from a noninvasive transdermal patch of the present
invention with results obtained from capillary blood glucose
utilizing standard method;
[0084] FIG. 41 is a plot of data which compares the results
obtained from a noninvasive transdermal patch of the present
invention with results obtained from capillary blood glucose
utilizing standard method;
[0085] FIG. 42 is a plot of data which compares the results
obtained from a noninvasive transdermal patch of the present
invention with results obtained from capillary blood glucose
utilizing standard method;
[0086] FIG. 43 is a plot of data which compares the results
obtained from a noninvasive transdermal patch of the present
invention with results obtained from capillary blood glucose
utilizing standard method;
[0087] FIG. 44 is a plot of data which compares the results
obtained from a noninvasive transdermal patch of the present
invention with results obtained from capillary blood glucose
utilizing standard method;
[0088] FIG. 45 is a plot of data which compares the results
obtained from a noninvasive transdermal patch of the present
invention with results obtained from capillary blood glucose
utilizing standard method;
[0089] FIG. 46 is a bar graph of data showing the effectiveness of
different gels without the use of wipes in noninvasive transdermal
glucose patches of the present invention;
[0090] FIG. 47 is a perspective views of a testing strip, which
develops a color shade indicative of a detected analyte of interest
presence within a patient;
[0091] FIGS. 48A and 48B are top and side views, respectively, of a
hand-held reflectometer suitable for reading developed color shade
on the transdermal patch of FIGS. 1A, 1B and 1C;
[0092] FIG. 49 is a cross-sectional view of the sensor head of the
hand-held reflectometer shown in FIGS. 48A and 48B;
[0093] FIG. 50 is a perspective view of a desk-top reflectometer
suitable for reading developed color shade on the testing strip of
FIG. 47;
[0094] FIG. 51 is a cross-sectional view of the reading site of the
desk-top reflectometer shown in FIG. 47;
[0095] FIGS. 52A and 52B are block diagrams of an electronic
circuit for two embodiments of a reflectometer in accordance with
the present invention;
[0096] FIGS. 53A and 53B are circuit diagrams for an analog portion
of the reflectometer of the present invention as shown in FIGS. 52A
and 52B, respectively;
[0097] FIGS. 54A and 54B are waveform diagrams illustrating
operation of a synchronous detector of the present invention;
[0098] FIGS. 55A and 55B are circuit diagrams illustrating
alternative implementations for providing temperature indicative
data to a reflectometer;
[0099] FIG. 56 is a diagram illustrating an exemplary operation of
the peak hold detection algorithm used in processing a signal
representative of the detected light;
[0100] FIG. 57 illustrates a lookup table which correlates a
certain voltage indicative of detected target surface color and
shade to a certain concentration of an analyte of interest;
[0101] FIG. 58A is a cross-sectional view illustrating an improper
engagement of the reflectometer sensor head and the transdermal
patch due to excessive pressure;
[0102] FIG. 58B is a cross-sectional view illustrating the use of a
window on the nose portion of the reflectometer sensor head to
ensure accurate positioning of the reflectometer with respect to
the target surface;
[0103] FIG. 58C is a cross-sectional view illustrating the use of a
tapered nose portion for the reflectometer sensor head;
[0104] FIG. 59 is a flow diagram illustrating the peak hold
detection algorithm used in processing a signal representative of
the detected light;
[0105] FIG. 60 is a flow diagram illustrating a process for
performing a first order calibration of the reflectometer;
[0106] FIG. 61 is a flow diagram illustrating a process for
performing a second and third order calibration of the
reflectometer;
[0107] FIG. 62 is a graph illustrating an exemplary compensated
voltage-analyte concentration curve and the affect thereon of the
first, second and third order calibration processes of FIGS. 60 and
61, respectively; and
[0108] FIG. 63 is a flow diagram illustrating a process for
converting an input voltage indicative of read color shade into a
concentration value output.
DETAILED DESCRIPTION
[0109] By way of illustrating and providing a more complete
appreciation of the present invention and many of the attendant
advantages thereof, the following detailed description and examples
are given concerning the novel methods, formulations and
configurations.
[0110] Referring now to the FIGS. in detail and first, particularly
to FIGS. 1A, 1B, 1C and 2 thereof, there is depicted an exemplary
noninvasive transdermal patch of a multi-layer composite
construction in accordance with the present invention, designated
generally as 1, which is in a rounded rectangle clam shell shape.
The noninvasive transdermal patch 1 includes two separate housing
30, 32 and an outer pulltab layer 4 on the frontal side of device
1. Therefore, patches of similar shapes, such as rectangular-shaped
patches with square corners, are likewise contemplated by the
present invention. The outer pulltab layer 4 and separate housing
30 and 32 function to keep the wet chemistry component 10 and the
dry chemistry component 20 separate from one another, dry and
uncontaminated during non-use. The outer pulltab layer 4 also
functions on the upper-outer most protective layer to which a
pressure sensitive adhesive layer 5 is affixed. The outer pulltab
layer 4 may be formed of an air, moisture and light barrier
material, such as a pink foil supplied by 3M Pharm. under the name
Scotch Pak, product number 1006 KG90008, which is about 0.010
inches thick. The adhesive layer 5 may be a pressure sensitive
adhesive, such as a double coated Medium tape on liner, product
number 3M 1522796A and obtained from Sunshine Tape, which is
approximately 0.005 inches in thickness. Adhered to the outer
pulltab layer 4 are two separate housings 30, 32, each connected by
hinge 35. Housing 30 contains a through aperture 31 for receiving
and maintaining the wet chemistry component 10, whereas housing 32
includes a through aperture 33 for visualizing the dry chemistry
component 20, as depicted in FIG. 1B and FIG. 2. As indicated
above, aperture 33 should be of such a dimension and the reading
head should be so configured that they interface precisely during
use to maximize the reflectometer's ability to read the color
intensity to detect the analyte. In addition to receiving wet
chemistry 10 in through aperture 31 of housing 30, housing 30
functions to maintain the wet chemistry component 10 in aperture
31, so that the wet chemistry component 10 remains in contact with
the dry chemistry component 20 during use. In this regard, it
should be appreciated that the gels of the present invention should
be formulated with a gel consistency sufficient to keep the gel in
the aperture 31 during storage and use and to permit the analyte to
pass through to the dry membrane for detection. Thus, if the gels
of the present invention are too viscous, they will interfere with
detection. On the other hand, if the gels are not sufficiently
viscous, they will simply leak out of and away from the patch
during testing, thereby preventing detection of the analyte.
[0111] The function of through aperture 33 in housing 32 is to
permit visualization of the chemical reaction based on the
differential colorimetric chemistry employed for a given analyte.
In addition, through aperture 33 of housing 32 functions to receive
the electronic interpretation component, such as a reflectance
spectrophotometer, for visualizing the test reaction based upon the
differential calorimetric chemistry electronically, as indicated
above. While the dimensions of through apertures 31 and 33 may be
of any suitable size, an exemplary size in accordance with the
present invention is about 3/16 to about 4/16 inches in diameter.
Preferably, housings 30 and 32 are manufactured with a cross-linked
closed cell sponge impervious to moisture. More particularly, the
cross-link closed cell sponge is a polyethylene foam, 12 lb
density, type A, product number GL-187 acrylic psa, supplied by 3M
Pharm. Alternatively, housings 30, 32 can be made of any other
suitable materials such as nylon, rubber, etc.
[0112] Affixed to each housing 30, 32 is a continuous white mylar
sheet 40 via adhesive 41. A suitable white mylar sheet is Dermaflex
PM 500 supplied by Flexcon Co., Inc. The Dermaflex PM 500 is a
white mylar sheet coated with TC200 to make it more printable and
adhesive #525. Sandwiched between white mylar sheet 40 and housing
32 is a dry chemistry membrane 20. Adjacent the surface of white
mylar membrane 40 and in contact with the dry chemistry membrane 20
is adhesive #525 of the Dermaflex PM 500 mylar sheet material. The
Dermaflex PM 500 white nylon sheet is also coated on both sides
with adhesive #525. White mylar sheet 40 is of a thickness of about
0.05 inches including the 50K6 liner. The white mylar sheet 40 is
equipped with through apertures 55 and 56. Through apertures 55 and
56 permit the wet chemistry component 10 to be in continuous
contact with the dry chemistry membrane 20 when housings 30 and 32
are folded together at hinge 35, as depicted in FIG. 3A. Affixed to
the dorsal side 41 of white mylar sheet 40 is a bottom pull cover
70. Bottom pull cover 70, like outer pulltab layer 4, is formed of
a similar pink foil which also functions as an air, moisture and
light barrier.
[0113] To use the noninvasive transdermal patch 1, as depicted in
FIGS. 1A, 1B and 1C, the subject preferably first cleans the area
of skin to which the test patch device is to be applied. The skin
may be cleansed with, for example, deionized water by rinsing. Once
the area of skin is properly and thoroughly cleansed and dried, a
skin permeation enhancer may be directly applied to the cleansed
area. As indicated hereinabove, however, if a skin permeation
enhancer is embodied into the wet chemistry component 10, it is not
necessary to also apply a skin penetrator to the skin. Before
applying the noninvasive transdermal patch 1 to the cleansed skin
area, both outer pulltab 4 and bottom pulltab cover 70 are removed.
Once outer pulltab 4 and bottom pulltab cover 70 are removed,
housings 30 and 32 are folded along hinge 35, so that dorsal
surfaces 36, 37 of housings 30, 32, respectively, are brought into
direct contact with one another, so that the wet chemistry
component 10 is now in contact with the dry chemistry membrane 20,
as depicted in FIG. 1C, to ensure continuous and uniform wetting of
the dry chemistry component or super sensitive or conditioned
membrane 20. In other words, through aperture 31 of housing 30 and
through aperture 33 of housing 32 are now in perfect alignment.
Frontal surface 38 of housing 30 is then directly applied to the
cleansed skin area, so that the wet chemistry component 10 is in
constant contact with the cleansed skin area during testing for
transferring the analyte from the biological fluid within or
underneath the skin, such as the interstitial fluid, to the dry
chemistry membrane 20 for chemical reaction indicator molecular
formation and analyte detection. While depicted in FIG. 1A, 1B or
1C, frontal surface 38 may include a pressure sensitive adhesive
for adhering the patch to the skin during testing.
[0114] Exemplary dimensions of the noninvasive transdermal patch 1,
when in a folded operable condition as depicted in FIG. 1C, are as
follows. The width is approximately 0.750 inches and the length is
about 0.75 inches, the diameter of the through apertures 31, 33 is
between about 0.1875 and 0.25 inches, and the height or thickness
is about 0.125 inches.
[0115] Alternatively, the rounded rectangle clam shell shaped
noninvasive transdermal patch 1 may further include bottom and top
pulltabs 80, 81, respectively, sandwiched between the outer pulltab
layer 4 and frontal surface 38 of housing 30 and frontal surface 39
of housing 32 as depicted in FIG. 2. When such top and bottom
pulltabs 80, 81 are utilized, the sequence of events during use is
as follows. Following skin cleaning, the outer pulltab layer 4 and
the bottom pulltab cover 70 are removed as before. However, the
bottom pulltab 80 is then removed and frontal surface 38 of housing
30 is applied to the cleansed skin area. After a period of time of
about 3 to about 15 minutes, top pulltab 81 is removed and the
formal indicator molecule (color change) is observed either
visually by the user or by an electronic detector component to
confirm the presence of the analyte, as described herein before.
The bottom and top pulltabs 80, 81 may also be made of a similar
white mylar sheet material as membrane 40 referenced above.
[0116] While the patches depicted in FIGS. 1A, 1B and 1C are
rectangular in shape with rounded corners, the patches of FIGS. 1A,
1B and 1C are exemplary of patches contemplated by the present
invention.
[0117] While there is no set length of time which the noninvasive
transdermal test patch devices of the present invention must be
applied, it is generally believed that a time of about 3 to about
15 minutes, and preferably from about 4 to 6 minutes, and most
preferably about 5 minutes is believed to be sufficient to develop
proper analyte transfer and reaction for reliable detection and
quantification. Moreover, while the noninvasive transdermal patches
of the present invention can be applied to any suitable skin area
from which an analyte of interest can be extracted from a
biological fluid within or underneath the skin, such as the arms,
under arms, behind ears, legs, inside portions of legs, fingertips,
torso, etc., it is preferable to place the noninvasive transdermal
patches on an area of skin free of hair, such as on the forearms
and, in particular, the right or left volar portions of the
forearm.
[0118] Configurations depicted in FIGS. 2-8 constitute further
alternative exemplary embodiments of noninvasive transdermal
patches of the present invention. For example, FIG. 3 depicts a
round-shaped flat patch comprising an outer shell 300 comprised of
a dry chemistry membrane 310 shown in the center of housing 320.
The dry chemistry component 310 is a membrane saturated with a
chemical reagent system for interaction and detection of an analyte
of interest. In use, the targeted skin area is precleansed and then
optionally treated with a skin permeation enhancer. Flat patch 300
is then removed from its foil packaging with desiccant (not shown)
and a selected wet chemistry gel component (not shown) is applied
on the back of membrane 310, which is then applied to the
pretreated skin area for a sufficient period of time to enhance
analyte transfer from the biological fluid within or beneath the
skin to the dry chemistry membrane 310 for analyte detection.
[0119] FIG. 4 depicts yet another example of a noninvasive
transdermal patch in accordance with the present invention. In FIG.
4, a clam shell patch 400 is disclosed which includes a top housing
410 and a bottom housing 420. Top housing 410 contains the dry
chemistry membrane 412 and bottom housing 420 contains the wet
chemistry component or gel 422. Housings 410 and 420 are preferably
connected by hinge 430 and each includes a concave interior surface
411 and 421, respectively, which complement one another. In use,
the targeted skin area is precleansed and optionally treated with a
skin permeation enhancer. Following skin pretreatment, the cover
(not shown) is removed from the clam shell patch 400 and it is
closed, so that the dry chemistry membrane 412 is in now contact
with the wet chemistry component or gel 422 to ensure continuous
and uniform wetting of the dry chemistry membrane 411. The bottom
423 of wet chemistry component or gel 422 is then applied to the
pretreated skin area for sufficient time to permit interaction
between the analyte under investigation and the chemical reagent
system saturated on the dry chemistry membrane 412 for analyte
detection.
[0120] Turning now to FIG. 5, it discloses a squeezer patch 500 in
accordance with the present invention, which comprises two separate
housings 510 and 520. Both housings 510 and 520 are circular in
shape and have concave interior surfaces 511 and 521, respectively,
which compliment one another. Housing 510 includes the dry
chemistry membrane 512 and housing 520 contains the wet chemistry
component 522. In addition, the wet chemistry component or gel 522
includes a small hole 523 which activates the chemistry when it is
squeezed. In use, the targeted skin area is precleansed and
optimally treated with a skin permeation enhancer. The squeezer
device 500 is removed from its foil packet with desiccant (not
shown), and housing 510 is inserted into housing 520, so that the
dry chemistry component 512 and the wet chemistry component or gel
522 are in contact with one another. The two housings 510 and 520
are squeezed to activate the chemistry and to continuously and
uniformly wet the dry chemistry membrane 512. The bottom of the wet
chemistry component or gel 512 is applied to the pretreated skin
area for a sufficient time to permit analyte transfer from the
biological fluid within or underneath the skin to the dry chemistry
membrane 512 for analyte detection.
[0121] FIG. 6 depicts, as a further alternative, a slider patch
600. In accordance with the present invention, slider patch 610
comprises top housing 610 and bottom housing 620. Pulltab 630 is
sandwiched between top and bottom housings 610 and 620,
respectively. Housing 610 includes the dry chemistry membrane 612
and bottom housing 610 contains the wet chemistry component or gel
622. Pulltab 630 can be made of any suitable material which
maintains an impenetrable barrier between dry chemistry membrane
612 and wet chemistry agents or gel 622 during nonuse. Preferably
the interior surfaces 611 and 621 of housings 610 and 620,
respectively, are concave in shape and match one another, so that
when pulltab 630 is removed, the dry chemistry component 612 and
the wet chemistry component 622 are in constant contact for
continuously and uniformly wetting the dry chemistry component 612.
To use, the targeted skin area is precleansed and pretreated with a
skin permeation enhancer, if necessary. The slider patch 600 is
then removed from the foil packet with desiccant (not shown) and
pulltab 630 is removed to activate the chemistry between the dry
and wet components 612 and 622, respectively. The bottom of the wet
chemistry component 623 is then applied to the pretreated skin area
for a sufficient amount of time for analyte detection of an analyte
in a biological fluid located within or beneath the skin.
[0122] In FIG. 7, a piercer patch 700 in accordance with the
present invention is illustrated. The piercer patch 700 comprises
housings 710 and 720 and piercer disk 730. Housing 710 includes a
dry chemistry membrane 712 and 720 contains the wet chemistry
component or gel 722. Piercer disk 730 includes sharp points 731
for nicking foil, into which the wet chemistry component 722 is
packed and stored (not shown), to release the wet chemistry
component 722 to continuously and uniformly wet the dry chemistry
membrane 712. The piercer disk 730 and sharp points 731 can be made
of any suitable material, such as metal or plastic. In use, piercer
patch 700 is removed from the foil packet with desiccant (not
shown) and the targeted skill area is precleansed and, optionally,
pretreated with a skin permeation enhancer. The piercer patch 700
is activated by pressing housings 710 and 720 together so that the
sharp points pierce the foil (not shown) between housings 710 and
720 to release the wet chemistry components in contact with one
another. The bottom surface of the wet chemistry component 722 is
then applied to the skin area for a sufficient period of time for
analyte detection.
[0123] Turning now to FIG. 8, it discloses a radial flow
immunoassay patch 800 which comprises two separate housing 810 and
820. Both housings 810 and 820 are circular in shape and have
concave interior surfaces 811 and 821, respectively, which
compliment one another. Housing 810 includes the dry chemistry
membrane 812 and a donut 813 of absorbent material, such as
diagnostic paper, #470, supplied by Schleichr and Schull, and
housing 820 contains the wet chemistry component 822. Wet chemistry
component 822 is pre-wet with a conjugate disk monoclonal antibody
such as anti-BHCG. In addition, the dry chemistry component or gel
812 includes a small spot of antibody, such as AHCG, thereon for
detecting the antigen. In use, the targeted skin area is
precleansed and optimally treated with a skin permeation enhancer.
The device 800 is removed from its foil packet with desiccant (not
shown), and housing 810 is inserted into housing 520 so that the
wet chemistry component 812 and the wet chemistry component or gel
822 are in contact with one another. The two housing 810 and 820
are squeezed together to activate the chemistry component 812. The
bottom of the wet chemistry component or gel 812 is applied to the
pretreated skin area for a sufficient time to permit analyte
transfer from the biological fluid within or underneath the skin to
the dry chemistry membrane 812 for analyte detection.
[0124] It should be understood to those of skill in the art that
the above alternative patches depicted in FIGS. 3-8 represent
examples of various patch configurations in accordance with the
present invention. It should be further understood that these
exemplary patch configurations do not constitute the only patch
variations contemplated by the present invention; but rather, the
present invention contemplates any patch configuration which
accomplishes the objectives of the instant invention. Moreover, it
should be understood that the exemplary patch configurations
depicted in FIGS. 3-8 can be made from, for example, the materials
and chemical reagent systems discussed herein or any other suitable
materials within the ambit of those skilled in this field.
[0125] As discussed above, the noninvasive transdermal systems of
the present invention include a wet chemistry component comprised
of a transfer medium which allows for liquid bridge transfer of an
analyte of interest from the biological fluid within or beneath the
skin to the dry chemistry component for biological reaction with
the chemical reagents to release or form a reporter or indicator
molecule (color change), which is indicative of the presence of the
analyte in the biological fluid. In accordance with the present
invention, the wet chemistry component is in the form of gel layer
and is present in the patch in an amount of about 20 mcls to about
35 mcls, and preferable in an amount of about 25 mcls. In a
preferred embodiment, the gel layer is a hydrophobic gel. A
preferred hydrophobic gel is one formed with carboxy polymethylene,
Carbopol.TM., in a concentration of from about 0.5% to about 2%. A
preferred hydrophobic gel in accordance with the present invention
is an about 1% carboxy polymethylene, Carbopol.TM. gel. It should
be appreciated that while a carboxy polymethylene gel matrix is
preferred, any other suitable gels prepared from, for example, 1%
carboxy methylcellulose, agarose, 10% glycerin and 1% carboxy
polymethylene in dH.sub.20, 10% polyethylene glycol in 1% carboxy
polymethylene in dH.sub.20, and 10% sodium lauryl sulfate and 1%
carboxy polymethylene in dH.sub.20, etc., may be utilized, so long
as they have the proper viscosity and do not interfere with analyte
transfer or detection.
[0126] In a further feature of the present invention, the wet
chemistry component may include a skin permeation enhancer.
Examples of skin permeation enhancers that may be included within
the wet chemistry component are propylene glycol, distilled water,
ionized water, DMSO, isopropyl alcohol, ethyl acetate, ethyl
alcohol, polyethylene glycol, carboxy methylcellulose,
1:1-water:acetonitride, 1:1:1-ethanol:propylene glycol:dH.sub.20,
1:1-ethanol:propylene glycol, 70:25:5-ethanol:dH.sub.20:olcic acid,
70:25:5-ethanol:dH.sub.20:isopropyl palmitate, 1:1-ethanol:water,
75% lactic acid in isopropyl alcohol, 90% lactic acid and 10%
Tween80 20% salicylic acid in 50% isopropyl alcohol in dH.sub.20,
1:1:1-ethyl acetate:isopropyl alcohol:dH.sub.20, etc.
[0127] In preparing the wet chemistry components or gels of the
present invention, it is generally preferable when making, for
example, a hydrophobic gel to sprinkle the hydrophobic, such as
carboxy polymethylene, slowly with slow mixing to avoid bubbles,
followed by deaeration by vacuum. Autoclave, when appropriate, may
be utilized for sterilization.
[0128] An especially preferred hydrophobic gel with a skin
permeation enhancer incorporated therein comprises about 1% carboxy
polymethylene, e.g., carbopol and about 10% propylene glycol. Such
a preferred hydrophobic gel can be prepared by slowly sprinkling
and mixing about 1 g of Carbopol.TM. 1342 (BF Goodrich) in a total
of about 100 ml of deionized water (18 meg ohm) containing about
10% propylene glycol. During mixing, bubbles should be avoided.
Following mixing, the gel is deaerated by vacuum.
[0129] It should be understood by those of skill in the art that
while transfer mediums containing skin permeation enhancers, are
preferred, it is not necessary to incorporate skin permeation
enhancers into the transfer medium. Alternatively, the present
invention envisions the use of transfer mediums, e.g., a
hydrophobic gel which is free of a skin permeation enhancer. An
example of such a transfer gel is a 1% carboxy polymethylene gel or
a 1% carboxy methylcellulose gel, as mentioned hereinabove.
Nevertheless, it should be understood, that when a skin permeation
enhancer is embodied into the transfer medium, the use of a
separate skin permeation enhancer on the skin prior to the
application of the noninvasive transdermal patch is optional.
However, when a transfer medium free of skin permeation enhancer is
selected, as the wet chemistry component 10 in accordance with the
present invention, the skin is preferably pretreated with a skin
permeation enhancer. A preferred skin permeation enhancer
contemplated by the present invention is propylene glycol or a
1:1:1 mixture of isopropyl alcohol, deionized water (18 meg ohm)
and ethyl acetate, which can be prepared by simply mixing the three
components together. Other skin permeation enhancers that may be
used in accordance with the present invention include DMSO, ethyl
alcohol, distilled water, deionized water (18 meg ohm), propylene
glycol, isopropyl alcohol, lactic acid, ethyl acetate, carboxyl
methylcellulose, Tween 80, salicylic acid (20% in deionozed
water/isopropyl alcohol--50/50), limonene, lactic acid 10% in
isopropyl alcohol, 90:5:5--isopropyl alcohol:Tween 80:limonene, 10%
lactic acid in isopropyl alcohol and 90% lactic acid and 10% Tween
80, etc. Of course, it should be understood that when a skin
permeation enhancer is selected, it should be applied to the skin
area, which will undergo testing in advance, in a sufficient
quantity and for a sufficient period of time prior to the
application of the noninvasive transdermal system, so that if the
skin permeation enhancer may act in an effective manner to assist
in the transfer of the analyte of interest in a biological fluid,
such as interstitial fluid, or detection by the dry chemistry
component 20 of the present invention. While the quantity and time
will vary depending upon the skin penetrant selected, the skin
permeation enhancer should be applied in an amount that will permit
it to rapidly dry within a short period of time to avoid excess
accumulation at the targeted skin site. It should also be
appreciated that when a skin permeation enhancer is selected for
use in accordance with the present invention, the analyte under
investigation should be taken into consideration so that a skin
penetrant is not selected which will somehow interfere with the
analyte of interest or its detection. For example, a cellulose-type
skin permeation enhancer may be possibly incompatible when the
analyte under investigation is glucose.
[0130] The dry chemistry component 20 of the present invention is
comprised of a novel super sensitive or conditioned membrane (a dry
chemistry membrane) which, in general, is approximately at least
100 times, and as much as 400-500 times, more sensitive than those
dry chemistry membranes currently used to detect an analyte in
whole blood. In fact, and quite surprisingly, it has been
discovered that, a super sensitive or conditioned membrane has the
ability to detect and quantify accurately and quickly the analyte
under investigation even though they are in very small
concentrations, e.g., about 5 mg/dl or 5 mcg/ml, in small volumes,
such as in a 25 mcl sample. Moreover, the sensors of the present
invention have the ability to detect analytes in sample sizes
generally to small for detection by HPLC methods. Generally
speaking, in order for HPLC methods to detect analyte under
investigation, it is believed that a sample size of at least about
200 mcl is needed. While any suitable material may be utilized as
the base material for the super sensitive or conditioned membranes
of the present invention, such as mylar materials, like BioDyne A
or BioDyne B supplied by Paul Gelman, an especially preferred
material is polyether sulfone distributed under the product name
Supor 450.TM. by Gelman Sciences. This particular polyether sulfone
material has a pore size of about 0.45 microns. While this
particular polyether sulfone material is preferred, it is
nevertheless believed that other polyether sulfone materials may be
utilized, such as nylon, having a pore size of about 0.8
microns.
[0131] A typical super sensitive or conditioned membrane in
accordance with the present invention comprises a glucose reactive
formulation for a noninvasive transdermal glucose patch. The
glucose reactive formulation comprises a base preparation and an
enzyme component as follows:
TABLE-US-00001 Glucose Reactive Formulation for Glucose Patch Base
preparation. 100 ml 6.0 gm Polyvinyl Pyrrolidinone K-30 [mw40,000]
(Sigma Chemical) 1.2 gm Citric Acid Trisodium Salt (Aldirch) 0.10
gm Citric Acid Monohydrate 0.028 gm NaBH4 [Sodium Borohidrate] 0.10
gm Bovine Serum Albumine [BSA] 0.545 gm O-Tolidine (Sigma Chemical)
adjust pH to 5.9-6.0 Add 2.0 ml 10% Gantrez S-95, 2 Butendonic
[10/0 gm/100 ml] (ISP Technologies) adjust pH to 5.9-6.0 with NaOH
4.0 gm/L 75% Dioctylsulfosuccinate DOSS[0.533 gm] (Sigma Chemical)
121.0 mg Glucose Oxidase (GOD) 150 u/ml[150u 100 ml/124 u/mg] (Fynn
Sugar) 38.53 mg Horse Radish Peroxidase (POD) 100 u/ml [100u 100
ml/259.55 u/mg] (Worthington)
[0132] The glucose reactive formulation can be prepared as follows.
First, prepare the base preparation by intimately mixing the
ingredients recited above with one another. Second, mix O-Tolidine
in deionized water until dissolved. Third, prepare an enzyme
solution as follows. Into a clean suitable sized container, measure
the calculated enzyme solution. Slowly add the prepared O-Tolidine
to the base solution while mixing until solution is clear. While
mixing, add the 20% Gantrex and mix for approximately 15-20
minutes. Thereafter add the DOSS while mixing and continue to mix
for an additional 15-10 minutes. Adjust the pH using NaOH to
6.8-6.9. At this point, solution should be clear. Thereafter, add
GOD to the clear solution while mixing. Once the GOD has been
added, stop mixing and add the POD. Once the POD is dissolved, mix
for an additional 15-20 minutes. The glucose reactive solution is
now ready for use. During preparation, the mixing should be done in
such a way to prevent foaming, so as to avoid denaturing the BSA.
It should be appreciated by those of skill in the art that because
the glucose reactive formulation contains excessive quantities of
both the enzymes and chromophore, O-Tolidine, the base preparation
is needed in the preparation to dissolve the excessive amounts of
the chromophore, O-Tolidine, and enzymes.
[0133] A super sensitive or conditioned glucose reactive membrane
may be prepared as follows. A sheet of the polyether sulfone or
other material is submerged into the glucose reactive solution as
prepared above, at an angle of about 45.degree. to drive air out of
the membrane material while introducing the glucose reactive
solution into the membrane material. Slowly pull the membrane
material through the solution to saturate the membrane material.
The wet, saturated membrane material is then dried by passing it
through a conventional 10 foot-long drier at a temperature of less
than about 41.degree. C. at a speed of about 2 feet/minute or for
about 5 minutes. Once dried, the top and bottom ends of the super
sensitive or conditioned membrane should be removed because of the
unevenness of the saturation at the top and bottom ends. The super
sensitive or conditioned membrane is now available for use as the
dry chemistry membrane 20 of the present invention.
[0134] An alternative glucose reactive membrane may be prepared as
follows:
[0135] Dry chemistry strips are prepared, in accordance with the
process of this invention, from the following materials and
reagents in similar concentrations as noted above: [0136] (a)
Membrane [0137] 1.) Gelman Sciences, Ann Arbor, Mich.,
Polyethersulfone (Supor) Porosity 0.22-0.8 microns [0138] (b)
Indicator about 1% (w/w) aqueous solution deionized water (18 meg
ohm) O-Tolidine hydrochloride [0139] (c) Glucose Specific Reagent
Cocktail [0140] 1.) glucose oxidate 125 IU activity per ml [0141]
2.) peroxidase 50 IU of activity per ml [0142] 3.) albumin 0.2%
(w/v) (enzyme stabilizer) [0143] (d) conditioning and flow control
agents--polyvinyl pyrolidone 3% (w/v) dioctylsulfosuccinate 0.2%
and 2 Butendioic acid polymer (0.35%) all buffered with 0.1 m
citrate, (pH 6.4)
[0144] Each of the above reagents are prepared fresh from reagent
grade chemical and deionized water. The base preparation is first
prepared by mixing the components together. The indicator is then
added followed by the cocktail. Once prepared, the membrane is
dipped briefly (about 30 seconds) into it until uniformly wetted.
It is then air dried at 37.degree. C. for about 15 minutes. The
dried membrane is stored with desiccant protected from moisture and
light. This dry chemistry membrane is cut into strips and can be
encapsulated, (i.e. glued) within the fold of an adhesive coated
mylar that is then affixed within the device. It is believed that
when this alternative glucose formulation and process are selected,
approximately 5 liters will effectively coat about 200 sq. Ft. of a
membrane, such as a BioDyne A membrane.
[0145] It has been surprisingly found that the above described
glucose reactive membranes have the unique ability to detect as
little as about 5 mg/dl or 5 mcg/ml of glucose which has diffused
from the interstitial fluid into the wet chemistry component. It
can now be readily appreciated by those of skill in this art that
the novel noninvasive transdermal patches of the present invention
are quite capable of accurately, reliably and quantitatively
detecting glucose in a subject. Moreover, the novel noninvasive
transdermal patches of the present invention are simple and easy to
use by nonmedically trained personnel while eliminating the need
for invasive, painful techniques utilized heretofore. Those skilled
in this art should therefore readily appreciate that the novel
noninvasive transdermal patches of the present invention provide a
significant advancement over the prior systems and techniques
concerning the body fluid analyte collecting and detection.
[0146] While the dry chemistry membrane 20 of the present invention
is described herein with particular reference to a certain glucose
membranes, it should nevertheless be understood that any other
suitable membrane may be employed in accordance with the present
invention, such as those described and illustrated in U.S. Pat. No.
4,774,192, which is incorporated herein by reference in its
entirety. It should also be understood by those of skill in the art
that, while the above-discussed super sensitive or conditioned
membranes are prepared with the chromophore, O-Tolidine, any other
suitable chromophore, such as tetra-methyl benzidine (TMB), may be
employed. It should further be appreciated that other indicator
systems, such as fluorophores or polarographic or enzyme
electrodes, may be employed to detect the analytes with the
noninvasive systems of the present invention, so long as the
objectives of the instant invention are not defeated.
[0147] Moreover, it should be understood by those of skill in the
art, that the above-discussion, with respect to glucose analysis of
interstitial fluid, can by analogy be readily extrapolated to the
preparation of super sensitive or conditioned membranes and
performance of clinical assays for the detection of a wide variety
of other analytes typically found in biological fluid samples, such
as interstitial fluid. The super sensitive or conditioned membrane
systems of this invention are, thus, applicable to clinical
analysis of, for example, cholesterol, triglycerides, bilirubin,
creatinine, urea, alpha-amylase, L-lactic acid, alanine
aminotransferase (ALT/GPT), aspartate aminotransferase (AST/GOT),
albumin, uric acid, fructose amine, potassium, sodium, chloride,
pyruvate dehydrogenase, phenylalaminehydroxylase, purine nucleotide
enzymes and phenylalanine hydroxylase or its substrates, such as
phenyl-alanine, phenyl-pyruvate or phenyl-lactate, to name a few.
The assay format can be essentially the same as that described
previously for glucose, or optionally involve the combination of a
conditioned membrane/reagent system with one or more additional
lamina (i.e. spreading layer, radiation blocking layer,
semipermeable diffusion layer, etc.).
[0148] The preparation of a conditioned membrane, incorporating a
dry chemistry reagent system for each of the above analytes,
follows essentially the same process as described for preparation
of glucose specific dry chemistry reagent systems (e.g.
conditioning the membrane with a flow control agent and the
absorption of the indicator/reagent cocktail). The conditioning of
the membrane can, thus, occur prior to or concurrent with contact
of the membrane with one or more of the constituents of the dry
chemistry reagent systems.
[0149] Generally speaking, in an alanine aminotransferase (ALT/GPT)
assay, the enzyme reacts with alanine and alpha-ketoglutarate to
form pyruvate and glutamate. The pyruvate that forms reacts with
2,4-dinitro phenylhydrazine that is colored at 490-520 nm. High
levels of alanine aminotransferase are associated with hepatitis
and other liver diseases. In an aspartate aminotransferase
(AST/GOT) assay, the enzyme reacts with aspartate 1 and
2-oxoglutarate to form oxaloacetate and glutamate. The oxaloacetate
that forms reacts with 2,4-dinitro phenylhydrazine that is colored
at 490-520 nm. High levels of oxaloacetate are associated with
myocardial infarction hepatitis and other liver diseases as well as
muscular dystrophy dermatomyositis. In an albumin assay,
bromocresol purple binds quantitatively with human serum albumin
forming a stable complex with maximum absorbance at 600 nm. Low
levels of human serum albumin are associated with liver disease,
nephrotic syndrome, malnutrition and protein enteropathies. High
levels of human serum albumin are consistent with dehydration.
Prealbumin may be of diagnostic value for diabetes and
malnutrition. Normal values are 3-5 gm/dl (30-50 gm/L). Critical
limits for children are lows of 10-25 gm/L or highs of 60-80 gm/L.
In a bilirubin assay, diazotized sulfanilic acid reacts
quantitatively with conjugated bilirubin forming azobilirubin with
maximum absorbance at 560 nm. High levels of bilirubin are
associated with biliary obstruction and hepatocellular disease. In
the presence of dimethyl sulfoxide (DMSO) both conjugated (direct)
and unconjugated (free), bilirubin reacts and is then indicative of
hemolytic disorders in adults and newborns. Critical limits for
adults are highs of 5-30 mg/dl (86-513 micromol/L) and 86-342
micromol/L for children; normal levels are up to 0.3 mg/dl serum
conjugated, but 1-12 mg/dl (96-308 micromol/L) for newborns.
Patches in accordance with the present invention, after a few
minutes, would read 1/50th of these values. In a chloride assay,
mercuric thioisocyanate reacts with chloride ions to give mercuric
chloride, the thiocyanate produced reacts with iron to give a
reddish brown product. Low levels of chloride ions are associated
with gastrointestinal or salt losing nephritis, Addisons disease.
High levels are associated with heart failure and Cushing's
syndrome. The critical limits are 60-90 mmol/L ( 1/50th of that is
to be expected in a patch of the present invention). Normal levels
are 95-103 mEq./L). In a cholesterol, total assay, cholesterol
esters are reacted with cholesterol esterase. The total free
cholesterol is further reacted with cholesterol oxides which in
turn generates peroxide detected with peroxidase coupled to a
colored dye O-Tolidine. Increased levels of cholesterol are
associated with atherosclerosis, nephrosis, diabetes mellitus,
myxedema, and obstructive jaundice. Decreased levels of cholesterol
are observed in hyperthyroidism, anemia, malabsorption and wasting
syndromes. Normal values are 150-250 mg/dl. (varies with diet and
age). Values above 200 mg/dl would suggest consulting a physician.
In a fructose amine assay, fructose amine reduces nitrotetrazolium
blue at alkaline pH. Fructose amine is useful in the management of
diabetes mellitus. Levels are indicative of glucose control. In a
lactic acid assay, porcine lactate dehydrogenase (Boehringer
Mannehim) reacts with lactate in the presence of nicotinamide
adenine dinucleotide (NAD) to produce NADH (NAD reduced) plus
pyruvate. The NADH is then detected by using the enzyme diaphorase
(Unitika) to react with a tetrazolium salt producing a colored
formazan. The color produced is directly proportional to the lactic
acid concentration. Lactic acid is useful in critical care
situations, as a measure of the success of supportive therapies to
predict the mortality rate. High levels correlate with severity of
clinical outcome. Blood lactate has become a prognostic indicator
of survival in patients with acute myocardial infarction and is
also used as an indicator of severe neonatal asphyxia. Lactic
acidosis is also found in patients with diabetes mellitus and
hepatic failure. Can be used in sports medicine to evaluate
endurance and fitness. Normal values are 5-20 mg/dl in venous
blood; lower (3-7 mg/dl) in arterial blood. Critical limits are
highs of 20.7-45 mg/dl (2.3-5.0 mmol/L). In a potassium assay, ion
specific electrodes have become stable and sensitive enough to be
used to detect the levels expected in a patch (critical limits are
1/50th of that found in the blood: i.e., 0.05-0.07 mmol/L) after a
few minutes skin contact. Potassium is useful in critical care
situations as a measure of the success of supportive therapies to
predict the mortality rate. High levels of potassium correlate with
severity of clinical outcome. Blood potassium has become a
prognostic indicator of survival in patients with acute myocardial
infarction. The normal values are 3.8-5.0 mEq./L (same as mmol/L)
in plasma; critical limits are low 2.5-3.6 mmol/L or high of 5-8
mmol/L. In a sodium assay, ion specific electrodes have become
stable and sensitive enough to be used to detect the levels
expected in a patch (critical limits are 1/50th of that found in
the blood after a few minutes skin contact. The normal values are
136-142 mEq./L (same as mmol/L) in plasma; critical limits are low
of 110-137 mmol/L or heights of 145-170 mmol/L. In a triglycerides
assay, triglycerides react with lipoprotein lipase giving glycerol
that when phosphorylated produces peroxide in the presence of
glycerol phosphate oxidate. This can be detected with a color dye
and peroxidase with the noninvasive transdermal systems of the
present invention. High levels of triglycerides are involved with
nephrotic syndrome, coronary artery disease, diabetes and liver
disease. Normal values are 10-190 mg/dl in serum. In an uric acid
assay, uric acid reacts with uricase to form allantoic and peroxide
that is detected by appropriate means. High levels of uric acid are
associated with gout, leukemia, toxemia of pregnancy and sever
renal impairment. Normal values are male 2.1-7.8 Mg./gl; female
2.0-6.4 mg/dl. The critical limits are a high of 10-15 mg/dl
(595-892 micromol/L).
[0150] Such examples of super sensitive or conditioned membranes
which can be made in accordance with the present invention are now
illustrated.
[0151] A super sensitive or conditioned membrane for urea can be
prepared by absorption into a conditioned membrane, of appropriate
concentrations of urease, buffer, and an indicator sensitive to
changes in pH. When a whole blood sample is brought in contact with
the sample receptive surface of the membrane, the serum is taken up
by the membrane. The urea present in the serum is digested by the
urease enzyme, thereby liberating ammonia in solution. The ammonia
can then react with a suitable indicator (i.e., a protonated
merocyanide dye). The pH of the membrane is buffered to about 8.0
to keep the equilibrium concentration of the ammonia relatively
low. The indicator is monitored at 520 nm. Additional details of
this specific reagent system are described in the open literature,
see for example Spayd, R. W. et al., Clin. Chem., 24(8):1343.
[0152] A super sensitive or conditioned membrane for alpha-amylase
can be prepared by absorption, into a conditioned membrane, of
appropriate concentrations of a derivatized substrate (i.e.,
starch) and buffer. When the whole blood sample is applied to the
sample receptive surface of the test strip, the serum is absorbed
into the membrane, thus, initiating digestion of the derivatized
substrate by the alpha-amylase in the sample. This digestion of the
substrate releases a chromophore or fluorophore which can be
monitored in accordance with accepted techniques and readily
available equipment. Additional details for this specific reagent
system also appear in the Spayd publication, previously referenced
herein.
[0153] A super sensitive or conditioned membrane for bilirubin can
be prepared by absorption, into a conditioned membrane, of
appropriate concentrations of certain cationic polymers (i.e.,
polymeric quaternary salts) and phosphate buffer (pH approximately
7.4). When an interstitial sample is applied to the sample
receptive surface of the test strip, the fluid is absorbed into the
membrane, thereby initiating interaction of the bilirubin and the
cationic polymer. Such interaction results in a shift in the
maximum absorption of the bilirubin from 440 to 460 nm with an
accompanying substantial increase in absorption at the new peak.
Additional details relating to this specific reagent system also
appear in the previously referenced Spayd publication.
[0154] A super sensitive or conditioned membrane for triglycerides
(triacylglycerols) can be prepared by absorption, into a
conditioned membrane, or surfactant, lipase, adenosine triphosphate
(ATP), glycerol kinase and L-alpha-glycerol phosphate oxidase, and
a triarylimidazole leuco dye. In brief, the surfactant aids in
dissociation of the lipoprotein complex so that the lipase can
react with the triglycerides for form glycerol and fatty acids. The
glycerol is then phosphorylated with the adenosine triphosphate in
the presence of the glycerol kinase enzyme. The L-alpha-glycerol
phosphate thus produced is then oxidized by the L-alpha-glycerol
phosphate oxidase to dihydroxy acetone phosphate and hydrogen
peroxide. The hydrogen peroxide oxidizes the lueco dye, producing a
colored indicator which has a peak absorption at 640 nm. Additional
details relating to this specific reagent system appear in the
previously referenced Spayd publication.
[0155] An alternative and preferred chemistry reagent system for
triglyceride analysis can be prepared by absorption, into a
conditioned membrane, of lipase, glycerol dehydrogenase,
p-iodonitrotetrozolium violet (INT) and diaphorase. The serum
triglycerides initially interact with the chemistry reagent system
and are hydrolyzed to free glycerol and fatty acids. The free
glycerol is now converted to the dihydroxyacetone by glycerol
dehydrogenase, in the presence of NAD. Simultaneous with such
conversion, INT (colorless) is reduced by diaphorase, in the
presence of NADH, to red dye (maximum gamma=500 mm). The change is
absorbance of the test strip at 500 nm is directly proportional to
the concentration of serum triglycerides.
[0156] A super sensitive or conditioned membrane for determination
of total cholesterol in interstitial fluid can be prepared by
absorption, into a conditioned membrane, of cholesterol ester
hydrolase, cholesterol oxidase, a leuco dye and peroxidase. Upon
application of a whole blood sample to the sample receptive surface
of the test strop, the serum is absorbed into the membrane, thereby
initiating conversion of the cholesterol esters to cholesterol, the
oxidation of the cholesterol is accomplished by the cholesterol
oxidase enzyme, thereby liberating peroxide. The peroxide and leuco
dye then interact in the presence of peroxidase to form a highly
colored indicator which can be monitored either visually or through
the use of instrumentation. Additional details relating to this
specific reagent system appear in the open literature, see Dappen,
G. N., et al. Clin. Chem., Vol 28, No. 5 (1982), 1159.
[0157] Alternatively, a super sensitive membrane for detection of
total cholesterol in interstitial fluid can be prepared, in
accordance with this invention, from the following materials and
reagents: [0158] (a) Membrane [0159] 1) Corning Costar, Cambridge,
Mass., Bioblot nylon plus Porosity 0.22-0.8 microns [0160] (b)
Indicator about 1% (w/w) aqueous solution deionized water
Tetramethylbenzidine [0161] (c) Cholesterol Specific Mixed Reagent
Cocktail [0162] 1) Cholesterol oxidase 150 IU activity per ml
[0163] 2) Cholesterol esterase 150 IU activity per ml [0164] 3)
peroxidase 50 IU of activity per ml [0165] 4) stabilizer for the
enzyme-albumin 0.2% (w/v) [0166] (d) conditioning and flow control
agents-polyvinyl pyrolidone 3% (w/v) and dioctylsulfosuccinate 0.2%
with 2 Butendioic acid polymer (0.35%) all buffered with 0.1 M
citrate, (pH 6.4).
[0167] Each of the above reagents are prepared fresh from reagent
grade chemical and deionized water. They are mixed together as one
homogenous solution and the membrane is dipped briefly (about 30
second) into it until uniformly wetted. This is then air dried at
about 37.degree. C. for about 15 minutes. This is stored with
desiccant protected from moisture and light. This dry chemistry
membrane is cut into strips and encapsulated, (i.e. glued) within
the fold of an adhesive coated mylar that is then affixed within
the device.
[0168] In yet another alternative, a super sensitive or conditioned
membrane for a cholesterol reactive formulation for cholesterol
detection can be prepared from the following enzymatic solution
preparation. The enzymatic solution preparation can then be
formulated with the base preparation as described earlier
hereinabove for the glucose reactive formulation for glucose
patch.
TABLE-US-00002 Cholesterol Enzymatic Solution Preparation To make
30 ml: O-TOLIDINE 5.45 gm/L 163.5 mg HORSERADISH 14.3 U/mg [259.55]
1.65 mg PEROXIDASE CHOLESTEROL OXIDASE 20.0 U/ml [25.1 U/mg] 23.9
mg CHOLESTEROL ESTERASE 60.5 U/mg 160.0 U/mg 11.34 mg
Once such a cholesterol reactive formulation is prepared, it can be
air dried onto a suitable membrane material, such as a polyether
sulfone membrane, Supor 450. supplied by Gelman Sciences or the
BioDyne A or BioDyne B membranes supplied by Paul Gelman, and used
with a wet chemistry component 10 of the present invention, such as
the hydrophobic gel comprising about 1% carboxy polymethylene and
about 10% propylene glycol.
[0169] A super sensitive or conditioned membrane for lactate
detection can be prepared from, for example, the following formula,
which is admixed with the base preparation described hereinabove
for the glucose reactive formulation for glucose patch, and then
saturated into a suitable membrane material such as a polyether
sulfane Supor 450 membrane supplied by Gelman Sciences or a BioDyne
A or BioDyne B membrane supplied by Paul Gelman.
TABLE-US-00003 Lactate Reactive Formula for Lactate Patch Based on
100 ml PVP K-30 6.0% K-PO.sub.4 0.15M BSA 0.10% LDH (rabbit muscle)
15000 U (Boehringer Mannehim) NAD 2.0 mM (Unitika) Diaphorase II
10000 U (Dojindo) WST4 (tetrazolium) 1.0 mM
[0170] A super sensitive or conditioned membrane for creatinine can
be prepared by absorption into a conditioned membrane of
appropriate concentrations of creatinine imino hydrolase and an
ammonia indicator (i.e., bromophenol blue). Upon application of an
interstitial fluid sample to the receptive surface of the membrane,
the interstitial fluid sample is absorbed into the membrane,
thereby initiating interaction of the creatinine and the enzyme,
creatinine amino hydrolase, resulting in the liberation of ammonia.
The ammonia thereby reacts with the indicator and the color
development monitored visually or with conventional
instrumentation. Additional details relating to this specific
reagent appear in the open literature, see for example Toffaietti,
J., et al., Clin. Chem., Vol. 29, No. 4 (1983), 684. It is also
contemplated that the dry chemistry reagent systems of this
invention be utilized in a multiple lamina test slide of the type
developed by Eastman Kodak Company of Rochester, N.Y. (Hereinafter
"Kodak format"). Where a permeable material (i.e. spreading layer)
is placed in contiguous contact with the sample receptive surface
of a treated membrane, such contract will influence (change) the
rate and quantity of interstitial fluid transported through the
membrane, and consequently the rate and extent of the reaction
mediated by the analyte specific components within the membrane. At
higher blood analyte levels the transport of sample across the
membrane can result in an overabundance of analyte and thus a
foreshortening of the usable range of measurement.
[0171] Also contemplated by the present invention is the adaptation
of the membrane to a displacement immunoassay of the type described
in Liotta U.S. Pat. No. 4,446,232, which is hereby incorporated by
reference in its entirety. In the configurations, the receptive
surface of the membrane is coated with an enzyme labeled antigen or
antibody (hereinafter "enzyme labeled conjugate"). The method of
application of the coating of the receptive surface insures against
penetration of the coating material into the matrix of the
membrane. The balance of the immunochemistry reagent system,
notably, a chromogenic or fluorogenic substrate for the enzyme is
incorporated into the conditioned membrane, so as to preserve its
physical isolation from the surface coating. The contact of the
sample with the coating on the surface of the membrane results in
displacement of enzyme labeled material. The displacement of the
enzyme labeled conjugate is based upon the dynamic equilibrium
which is caused by the presence of an analyte in the sample and the
competition with the conjugate for binding to an analyte mimic in
the surface coating.
[0172] This displaced enzyme labeled conjugate, along with a
portion of the fluid fraction of the sample, is absorbed in the
matrix of the membrane. The enzyme portion of this conjugate
interacts with a substrate specific for the enzyme and thereby
produces a discernible change in color or fluorescence which is
indicative of the analyte of interest. This change can be observed
visually, (in the case of color change) or by instrumentation
designed for that purpose.
[0173] In practicing the present invention, the targeted skin area
for testing should first be thoroughly cleansed. This can be
accomplished by washing the area thoroughly with water by rinsing
and then permitted to dry. Once cleansed, the skin permeation
enhancer, if separately utilized, should be applied to that area of
skin in a sufficient quantity and for a sufficient period of time.
Typically, there is no set amount, but the amount applied should be
effective as described herein. The time should be sufficient to
permit the skin permeation enhancer to penetrate the skin to assist
extraction of the body fluid such as interstitial fluid. This
generally takes only a few seconds. Of course, if a skin permeation
enhancer is selected, it should not in any way interfere with the
analyte under investigation. Thereafter, the noninvasive
transdermal system, such as the patch depicted in FIG. 1A, 1B, 1C
or 2, should be immediately applied, so that the wet chemistry
component 10 is in direct and continuous contact with the cleansed
skin area, which may or may not have been pretreated with a skin
permeation enhancer, and the dry chemistry component 20 is in
direct and continuous contact with the wet chemistry component 10.
Preferably, such application should be for a period of between
about 3 and 15 minutes, preferably between about 4 to about 6,
minutes and more preferably, about 5 minutes. Also, immediately
prior to skin application, the wet and dry chemistry components 10
and 20, respectively, should be placed in contact with one another
for purposes of continuously and uniformly wetting the dry
chemistry component 20, so that reliable analyte detection can be
made.
[0174] While not wishing to be limited to any particular theory or
mechanism of action, it is believed that the underlying mechanism
of the patch is as follows. First, chemicals in the patch
temporarily dissolve the lipid barrier of the skin which seals the
dead cells of the uppermost layer of the stratus corneum. This
results in a penetration of the stratus corneum by converting it
into a semi-permeable membrane through which the interstitial fluid
containing glucose is withdrawn. The glucose from the interstitial
fluid in combination with the patented transport medium, diffuses
through the skin to the site of the chemical reaction on the
membrane containing the glucose-specific reactants. After about 3-4
minutes, a biochemical equilibrium is reached resulting in an end
point color reaction which is measured optically by a highly
sensitive reflectance meter.
[0175] Reference is now made to FIGS. 1A, 1B and 1C and FIG. 2
wherein there is shown a perspective view of a transdermal patch 1
which develops a color shade indicative of the detected presence
within the body of an analyte of interest (and perhaps also its
concentration). As discussed herein-before, the patch 1 has a
rounded rectangular shape (as shown), but may also have other
shapes as desired, such as depicted in FIGS. 3-8. A top surface 32
of the patch 1 includes a generally circular opening 33 which
exposes a membrane 20 to view. In general, a bottom surface (not
shown) of the patch 1 includes an adhesive layer and may be affixed
to the skin of a patient. A certain analyte of interest is then
extracted from the skin and transported through a gel-like
transport medium to the membrane 20. At the membrane 20, a
biological and chemical reaction occurs with respect to the
extracted analyte of interest to develop a color indicator thereon
which is indicative of the presence within the body of the analyte.
The shade of the developed color indication may also be indicative
of analyte concentration level within the body. As an example, the
analyte of interest may relate to blood sugar, and thus the
developed color shade on the membrane would be indicative of
glucose level. Other analytes of interest could be extracted by the
patch 1 and used to develop color indications on the membrane 20
related to cholesterol, triglycerides, bilirubin, creatinine, urea,
alpha-amylase, L-lactic acid, alanine aminotransferase (ALT/GPT),
aspartate aminotransferase (AST/GOT), albumin, uric acid, fructose
amine, potassium, sodium, chloride, pyruvate dehydrogenase,
phenylalaninehydroxylase, purine nucleotide enzymes and
phenylalanine hydroxylase or its substrates such as phenyl-alanine,
phenyl-pyruvate or phenyl-lactate, to name a few.
[0176] Reference is now made to FIG. 47 wherein there is shown a
perspective view of a testing strip 2000 which develops a color
shade indicative of the presence within the body of an analyte of
interest (and perhaps also its concentration). The strip 2000 has a
generally rectangular shape. A top surface 2200 of the strip 2000
includes a testing region 2400. In general, a drop of bodily fluid
(such as blood, urine, saliva, perspiration, and the like) is
deposited on the testing region 2400. A biological and chemical
reaction occurs with respect to an analyte of interest within the
deposited fluid to develop a color indicator on the strip 2000
indicative of the presence within the body of the analyte. The
shade of the developed color indication may also be indicative of
analyte concentration level within the body. As an example, the
analyte of interest may relate to blood sugar, and thus the
developed color shade on the strip 2000 would be indicative of
glucose level. Other analytes of interest, such as those discussed
above with respect to the transdermal patch 1, could be processed
in the testing region 2400 and used to develop color indications
related to analyte concentrations.
[0177] Reference is now made to FIGS. 48A and 48B wherein there are
shown top and side views, respectively, of a hand-held
reflectometer 3000 suitable for reading developed color and shade
on the transdermal patch 1 of FIGS. 1A, 1B and 1C and FIG. 2. The
reflectometer 3000 includes a sensor head 3200 on one end of a
semi-cylindrical case 3400 that can be comfortably held in one
hand. A "READ" button 3600 activates the reflectometer 3000 to make
a measurement of color and shade at the sensor head 3200. A liquid
crystal display (LCD) 3800 provides numerical output to a user of
the reflectometer 3000 that is indicative of the color shade, such
as for example, a voltage level, or of some measurable quantity or
quality related to that read color shade, such as, for example, a
concentration level. The display 3800 may also provide other
important information to the user such as date and time of day. If
the display 3800 is capable of producing alphabetic and/or graphic
as well as numeric characters, the display may also be used to
provide messages to the user, perhaps relating to instructions for
use, error indications, icons, reminders, and the like. Two key
switches, a "SCROLL" button 4000 and a "SELECT" button 4200, are
located on the face of the reflectometer 3000. Utilizing these
buttons 4000 and 4200, the user may set date and time of day
information. These buttons 4000 and 4200 may further be utilized to
program alarms which alert the user as to when it is necessary to
take a reading. The user may still further utilize the buttons 4000
and 4200 to enter data into the reflectometer 3000 that is
necessary to ensure accurate measurement and information output. As
an example, the user may select a manufacturing batch code for the
transdermal patch 1, or input color/shade data for calibrating the
reflectometer 3000, or select the type of testing to be performed,
for example, glucose versus cholesterol. A battery compartment 4400
is located in the top end of the meter. An external port connection
(not shown) may also be provided to allow the user to connect the
reflectometer 3000 up to a personal computer or a telephone line or
an infra-red communications link in order to communicate readings.
The reflectometer 3000 further includes an opening 4600 for a
speaker (not shown) that may produce sounds such as alarm sounds
and data entry confirmation sounds.
[0178] Operation of reflectometer 3000 may be better understood by
presentation of the following example of its use with a transdermal
patch 1, such as that illustrated in FIGS. 1A, 1B and 1C and FIG.
2. Once applied to the skin, the transdermal patch 1 requires
approximately a three to five-minute incubation period, dependent
on number of factors including temperature. As an example, the
transdermal patch 1 is preferably attached to the skin on the
inside of the patient's forearm. Once the transdermal patch 1 is
applied to the skin, the user may depress the SELECT button 4200 to
start a user chosen, reflectometer calculated or pre-programmed
count-down period which measures the time required for incubation
and development of the color shade indicative of extracted analyte.
After the time expires, an audible alarm alerts the user that it is
now time to take a reading. A cylindrical shaped protruding nose
portion 4800 of the sensor head 3200, generally matching in size
and shape the circular shape of the opening 33, is then inserted
into the opening 33 of the transdermal patch 1 and positioned
adjacent the membrane 20. The user then depresses the "READ" button
3600 to power up the device and initiate reflectometer 3000
operation to detect and measure any developed color and shade
present on the membrane 20. Data such as a signal voltage level
relating to the detected color shade or an analyte concentration
relating to the detected color shade is then output for user
consideration on the display 3800. Alternatively or additionally,
this data may be output through the external port connection for
remote processing and analysis to inform the user of analyte
concentration information.
[0179] Reference is now made to FIG. 49 wherein there is shown a
cross-sectional view of the sensor head 3200 of the hand-held
reflectometer 3000 shown in FIGS. 48A and 48B. The sensor head 3200
contains a dual light source to increase the reflective signal
strength and to more uniformly illuminate the target surface of the
membrane 20 where the color and shade indicative of analyte
presence and concentration level is developed. Two light emitting
diodes (LEDs) 5000 are mounted in a housing 5200 at a certain angle
.THETA. to normal 5400 with respect to the membrane 20. The LEDs
5000 may be of any suitable color related to the color shades to be
detected. As an example, red LEDs 5000 with a wavelength of
approximately 637 nm have been found to produce excellent results
in detecting the color shades which develop on the membrane 20 from
the use of an appropriate chromophore or fluorophore indicator,
such as O-Tolidine, tetra-methyl benzine, and the like, during
glucose analyte testing. LEDs of other colors, such as green, or
perhaps infra-red may be used, perhaps in conjunction with the red
LEDs, depending on the selected chromophore or fluorophore
indicator. The housing 5200 is constructed with a low-expansion
plastic such as Ryton, preferably with a non-reflective surface,
and should be opaque as to the wavelength of the light source to
substantially eliminate any background signal from stray reflection
of light emitted from the LEDs 5000. The angle .THETA. may be any
angle that minimizes detection of specular reflection and is
preferably approximately forty to forty-five degrees. The LEDs 500
each have a relatively narrow (for example, fifteen degree)
projection angle with respect to their emitted light output. The
light output from the LEDs 5000 is directed along a light pipe (or
collimator) 5600 through an opening 5800 in the protruding nose
4800 portion of the sensor head 3200 to illuminate the target
surface. The position of the LEDs 5000 along the length of the
light pipe 5600 may be adjusted during fabrication of the
reflectometer to alter the intensity of target surface illumination
and the effects and instances of side reflections within the light
pipe. A photo transistor 6000 is mounted within the housing 5200
and oriented along the normal 5400 with respect to the target
surface of the membrane 20 for the transdermal patch 1. The photo
transistor 6000 similarly has a relatively narrow, for example,
fifteen degree, viewing angle. Reflected light emitted from the
target surface of the membrane 20 passes through the opening 5800
in the protruding nose 4800 portion of the sensor head 3200, and is
directed along a light pipe (or collimator) 6200 to the photo
transistor 6000. The position of the photo transistor 6000 along
the length of the light pipe 6200 may be adjusted during
fabrication of the reflectometer to alter the sensitivity and
tolerance of the reflectometer in reading target surface
illumination and color shade. Arrangement of the LEDs 5000 and
photo transistor 6000 in the illustrated angle .THETA. offset and
symmetrical orientation serves to minimize detection of specular
reflection off the target surface of the membrane 20 and reduce the
effect of rotational error about the normal 5400 that may result
from a slightly uneven illumination of the target surface.
[0180] Reference is now made to FIG. 50 wherein there is shown a
perspective view of a desk-top reflectometer 3000' suitable for
reading developed color shade on the testing strip 2000 of FIG. 47.
The reflectometer 3000' includes a reading site 3200'. A "READ"
button 3600 activates the reflectometer 3000' to make a measurement
of color shade at the reading site 3200'. A liquid crystal display
(LCD) 3800 provides numerical output to a user of the reflectometer
3000' that is indicative of the detected color shade or of some
measurable quantity or quality related to that read color shade.
The display 3800 may also provide other important information to
the user such date and time of day. If the display 3800 is capable
of producing alphabetic and/or graphic as well as numeric
characters, the display may also be used to provide messages to the
user, perhaps relating to instructions for use, error indications,
icons, reminders, and the like. Two key switches, a "SCROLL" button
4000 and a "SELECT" button 4200, are located on the face of the
reflectometer 3000'. Utilizing these buttons 4000 and 4200, the
user may set date and time of day information. These buttons 4000
and 4200 may further be utilized to program alarms which alert the
user as to when it is necessary to take a reading. The user may
still further utilize the buttons 4000 and 4200 to enter data into
the reflectometer 3000' that is necessary to ensure accurate
measurement and information output. As an example, the user may
select a manufacturing batch code for the testing strip 2000, or
input color/shade data for calibrating the reflectometer 3000', or
select the type of testing to be performed, for example, glucose
versus cholesterol. An external port connection (not shown) may be
provided to allow the user to connect the reflectometer 3000' up to
a personal computer or a telephone line or an infrared
communications link in order to communicate readings. The
reflectometer 3000' further includes an opening 4600 for a speaker
(not shown) that may produce sounds such as alarm sounds and data
entry confirmation sounds.
[0181] Operation of reflectometer 3000' may be better understood by
presentation of the following example of its use with a testing
strip 2000 such as that illustrated in FIG. 47. The reflectometer
3000' is activated and recognizes from detected voltage level
whether a testing strip is in place within a slot 7000. If not, the
reflectometer 3000' prompts the patient to insert a strip.
Responsive to insertion of a testing strip into the slot 7000, the
reflectometer 3000' prompts the patient to deposit a sufficient
amount of bodily fluid, such as blood, urine, saliva, perspiration,
and the like, is then deposited on the testing region 2400 of the
strip 2000. A biological and chemical reaction occurs with respect
to an analyte of interest within the deposited fluid to develop a
color indicator on the strip 2000 whose shade can be related to
analyte concentration levels. A timer is then initiated to measure
whether sufficient progress in the chemical reaction, based on
detected voltage level, occurs within a predetermined first time
period, that may be user chosen, reflectometer calculated or
pre-programmed. If not, the patient is prompted to start the
testing process over with a new strip. If sufficient progress
occurs within this first time period, the timer then starts
measuring a second time period, that may be user chosen,
reflectometer calculated or pre-programmed, to detect completion of
the testing process. In one supported testing procedure, expiration
of the second time period initiates reflectometer 3000' operation
to detect and measure color shade on the strip 2000. Data such as a
signal voltage level relating to the developed color shade or an
analyte concentration relating to the developed color shade is then
output for user consideration on the display 3800. In another
supported testing procedure, the reflectometer 3000' operates to
measure a voltage level indicative of detected color shade on the
strip 2000. If the measured voltage level stabilizes before
expiration of the second time period, data such as a signal voltage
level relating to the developed color shade or an analyte
concentration relating to the developed color shade is then output
for user consideration on the display 3800. Alternatively or
additionally, the data may be output through the external port
connection for remote processing and analysis to inform the user of
analyte concentration information. In the event that either 1) the
measured voltage level does not stabilize, or 2) the measured
voltage level drops below an acceptable threshold, an error message
is displayed to prompt the patient to start the testing process
over with a new strip.
[0182] Reference is now made to FIG. 51 wherein there is shown a
cross-sectional view of the reading site 3200' of the desk-top
reflectometer 3000' shown in FIG. 50. The reading site 3200'
contains a dual light source to increase the reflective signal
strength and to more uniformly illuminate the target surface of the
strip 2000. Two light emitting diodes (LEDs) 5000 are mounted in a
housing 5200 at a certain angle .THETA. to normal 5400 with respect
to the strip 2000. The LEDs 5000 may be of any suitable color
related to the color shades to be detected. As an example, red LEDs
5000 with a wavelength of approximately 637 nm have been found to
produce excellent results in detecting the color shades which
develop on the strip 2000 from the use of an appropriate
chromophore or fluorophore indicator during cholesterol analyte
testing. LEDs of other colors, such as green, or perhaps infra-red
may be used, perhaps in conjunction with the red LEDs, depending on
the selected chromophore or fluorophore indicator. The housing 5200
is constructed with a low-expansion plastic such as Ryton,
preferably with a non-reflective surface, and should be opaque as
to the wavelength of the light source to substantially eliminate
any background signal from stray reflection of light emitted from
the LEDs 5000. The angle .THETA. may be any angle that minimizes
detection of specular reflection and is preferably approximately
forty to forty-five degrees. The LEDs 5000 each have a relatively
narrow, for example, fifteen degree, projection angle with respect
to their emitted light output. The light output from the LEDs 5000
is directed along a light pipe (or collimator) 5600 through an
opening 5800 in the top 7200 of the reflectometer case along the
slot 7000. The position of the LEDs 5000 along the length of the
light pipe 5600 may be adjusted during fabrication of the
reflectometer to alter the intensity of target surface illumination
and the effects and instances of side reflections within the light
pipe. A photo transistor 6000 is mounted within the housing 5200
and oriented along the normal 5400 with respect to the target
surface of the strip 2000. The photo transistor 6000 similarly has
a relatively narrow, for example, fifteen degree, viewing angle.
Light emitted from the target surface of the strip 2000 passes
through the opening 5800, and is directed along a light pipe (or
collimator) 6200 to the photo transistor 6000. The position of the
photo transistor 6000 along the length of the light pipe 6200 may
be adjusted during fabrication of the reflectometer to alter the
sensitivity and tolerance of reflectometer in reading target
surface illumination and color shade. Arrangement of the LEDs 5000
and photo transistor 6000 in the illustrated angle .THETA. offset
and symmetrical orientation serves to minimize specular reflection
off the target surface of the strip 2000 and reduce any adverse
effects arising from a slightly uneven illumination of the target
surface.
[0183] Reference is now made to FIGS. 52A and 52B wherein there are
shown block diagrams for two embodiments of an electronic circuit
for the reflectometer 3000/3000' in accordance with the present
invention. A light source 10000 is driven by a square wave current
to emit pulses of light 10400 which illuminate a target surface
10600. In one embodiment, as shown in FIG. 52A, the square wave is
generated by an oscillator 10200. In another embodiment, as shown
in FIG. 52B, the square wave is generated by a microprocessor
14200. As shown in FIGS. 49 and 51, the light source may comprise a
pair of LEDs 5000 of the same or different colors. In situations
where different colors are used, the LEDs may be pulsed either
simultaneously or alternately. The pulses of light 10400 are output
from the light source 10000 with a frequency of seventy-five Hertz
and a duty cycle of fifty percent. Any frequency may be chosen
provided it does not comprise a harmonic or sub-harmonic of AC line
voltage, i.e., fifty or sixty Hertz, and is sufficiently high
enough to read the target surface and allow for a statistically
significant number of reflectivity samples to be taken within an
acceptably short measurement period. The target surface 10600 that
is illuminated by the light source 10000 may comprise, for example,
the membrane 2000 of a transdermal patch 1 like that shown in FIGS.
1A, 1B and 1C and FIG. 2 or the surface of a strip 2000 like that
shown in FIG. 47. Alternatively, any other substrate may be
illuminated by the light source 10000.
[0184] The illuminated target surface 10600 reflects the received
light 10400 and thus radiates light 10800 corresponding to the
developed color and shade on the target surface 10600 which is
detected by an optical detector 11000. As shown in FIGS. 49 and 51,
the optical detector 11000 may include a photo transistor 6000. The
optical detector 11000 generates in a differential amplifier
configuration a pair of differential outputs 11200 and 11600,
one-hundred and eighty degrees out of phase from each other, whose
peak-to-peak voltages are representative of the detected color and
shade of the target surface 10600. The pair of differential outputs
11200 and 11600 are applied to a differential (to unbalanced
conversion) amplifier 11400 to generate a single output signal
12200 whose peak-to-peak voltage is representative of the detected
color and shade of the target surface 10600. The second output
11600 of the optical detector 11000 is applied to a buffer 11800
before being applied to the differential amplifier 11400. The
buffer 11800 output is also applied to an integrator 12000 which
compares the signal to a reference voltage and integrates the
result of the comparison to generate a DC signal 16200 to bias the
optical detector 10000 back to its designed quiescent operating
point and thus compensate for any detected ambient (DC) background
light. The output 12200 of the differential amplifier 11400
accordingly provides a signal whose peak to peak voltage level is
indicative of the color and shade of the target surface, when the
light source is illuminated, as opposed to any color or shade that
relates to the effects of ambient DC light at the target surface,
when the light source is off.
[0185] The output 12200 of the differential amplifier 11400 is then
applied to a synchronous detector 12400. The synchronous detector
12400 also receives the light source 10000 drive signal which is
output from the oscillator 10200 and obtains information concerning
when the light source 10000 is illuminating, and not illuminating,
the target surface. As this illumination is being detected by the
optical detector 11000, and since the signal output 12200 from the
differential amplifier 11400 is affected by the detected
illumination, the synchronous detector 12400 may then process the
output 12200 to full wave rectify the signal output 12200 from the
differential amplifier 11400 and produce a substantially steady DC
voltage that is indicative of the color or shade of color at the
target surface. The output 12600 from the synchronous detector
12400 is then low pass filtered to remove any included high
frequency components resulting from the synchronous detection
process before any subsequent processing occurs.
[0186] Positioned adjacent to the light source 10000, perhaps with
some included thermo-mechanical coupling, is a temperature sensor
12800. The temperature sensor 12800 generates an output 13000 that
is indicative of temperature at or near the light source. This
information is important to consider in situations where the
brightness and intensity of the light 10400 emitted from the light
source 10000 varies with changes in temperature. Any experienced
brightness or intensity changes in the emitted light 104000 cause
corresponding changes in the output signal 12600. With knowledge of
temperature indicative information, appropriate actions can be
taken during subsequent processing of the signal 12600 output from
the synchronous detector 12400 in order to account for the
temperature driven variations in emitted light and the
corresponding variations in the output signal 12600.
[0187] Reference is now specifically made to FIG. 52A. In
accordance with a first embodiment of the present invention, the
previously described components of the reflectometer 3000/3000' are
contained within a case, such as the hand held or desk top units
described above. The reflectometer 3000/3000' outputs the signal
12600 and the signal 13000 through an external port connection
13200 and over a communications link 13400 to a personal computer
136, separate and apart from the case for the reflectometer
3000/3000', where the signal are processed. The communications link
13400 may comprise, for example, multi-wire cable if the
reflectometer 3000/3000' is proximately located to the personal
computer 13600, or a telephone line or infra-red transceiver if the
reflectometer is remotely located to the personal computer 13600. A
PC/MCIA card (not shown) may be utilized to interface the
reflectometer 30/30' to the personal computer 13600. It will, of
course, be understood that suitable equipment, not shown but well
known to those skilled in the art, must also be included to
interface the reflectometer 3000 to a telephone line. In the
personal computer 13600, the received signals 12600 and 13000 are
converted by a internal digital-to-analog converter 13800 to
digital values. These digital values are then processed by an
internal processing unit 14000 to generate information concerning
analyte concentration level. The detected concentration information
is then displayed by the personal computer 13600 on its display
screen and stored in computer memory for later retrieval,
consideration, analysis and transfer. In this embodiment, the
signals output from the "READ" button 3600, "SCROLL" button 4000
and "SELECT" button 4200, see FIG. 48A, of the reflectometer
3000/3000' are also transmitted through the external port
connection 13200 and over the communications link 13400 to the
personal computer 13600.
[0188] Reference is now specifically made to FIG. 52B. In
accordance with a second embodiment of the present invention, all
the required reading and processing components of the reflectometer
3000/3000' are advantageously contained within a case, such as the
hand held or desk top units described above. This provides for a
self-contained, portable device. The signal 12600 and the signal
13000 are presented to a microprocessor 14200 located within the
reflectometer 3000/3000' case. The microprocessor 14200 includes an
analog-to-digital conversion functionality 14400 for converting the
analog signals 12600 and 13000 to digital values. These digital
values are then processed by the microprocessor 14200 to generate
information concerning detected analyte concentration level. The
detected concentration information is then displayed by the
reflectometer 3000/3000' on the liquid crystal display 3800 and
stored in the microprocessor 14200 memory 14600 for later
retrieval, consideration and transfer. An external port connection
14800 is provided through the microprocessor 14000 in order to
allow for the communication of the detected concentration
information over a communications link 13400 to a personal computer
13600. The communications link 13400 may comprise, for example,
multi-wire cable if the reflectometer 3000/3000' is proximately
located to the personal computer 13600, or a telephone line if the
reflectometer is remotely located to the personal computer 13600.
Preferably, the microprocessor 14200 includes the appropriate
circuitry for interfacing the reflectometer 3000/3000' to a
telephone line. As an alternative, the microprocessor 14200 may
utilize the light source 10000 to allow for the communication of
the detected concentration information over an optical
communications link, such as an infra-red connection. In this
embodiment, the processor appropriately modulates the light source
with the detected concentration information to effectuate a data
communication.
[0189] The "READ" button 3600, "SCROLL" button 4000 and "SELECT"
button 4200, see FIG. 48A, are connected as inputs to the
microprocessor 14200. Using the "READ" button 36000, the user
activates the reflectometer 3000/3000' to make a measurement of
color shade. The liquid crystal display 3800 then provides a
numerical output to the user that is indicative of the color shade
or of some measurable quantity or quality related to that read
color shade. Using the "SCROLL" button 4000 and "SELECT" button
4200, the user may set date and time of day information, request
current date and time of day information, program alarms which
alert the user as to when it is necessary to take a reading, enter
reflectometer data, such as a manufacturing batch code for the
transdermal patch 1, or input color/shade data for calibrating the
reflectometer, and select the type of testing to be performed, for
example, glucose versus cholesterol. A speaker 15000 is connected
to the microprocessor 14200 to provide audible signals to the user,
such as an alarm.
[0190] Reference is now made to FIGS. 53A and 53B wherein there are
shown circuit diagrams for an analog portion of the reflectometer
of the present invention, as illustrated in FIGS. 52A and 52B,
respectively. The square wave oscillator 10200 in the embodiment of
FIG. 52A comprises a conventional LM555 timer integrated circuit
15100 configured with appropriately connected resistors and
capacitors to generate a square wave output on line 15200 at a
selected frequency, for example, about seventy-five Hertz, and with
a selected duty cycle, for example, about fifty percent.
Alternatively, the square wave is generated by the microprocessor
14200 in the embodiment of FIG. 52B and supplied by a buffer 10200'
for output on line 15200. The square wave output on line 15200 is
applied to a pair of series connected LEDs 5000, which emit pulses
of light, and a light level adjustment circuit 15400 comprising a
potentiometer 15600 within the light source 10000.
[0191] The adjustment provided through use of the potentiometer
comprises a factory performed adjustment to set the level or
intensity of pulsed light output from the LEDs 5000 for the
reflectometer 3000/3000'. More specifically, the adjustment
comprises a first order calibration of the reflectometer
3000/3000'. A more complete explanation of how this calibration
process is executed is provided below.
[0192] The modulated light is reflected from a target surface and
detected (with minimal spectrally reflected components) by the
optical detector 11000. This optical detector 11000 includes a
photo transistor 6000 differentially connected to another
transistor 15800, wherein the differentially connected photo
transistor and other transistor share substantially similar
operating characteristics. By differential connection it is meant
that the emitters of the photo transistor 6000 and the transistor
15800 are connected to each other. The base of the transistor 15800
is driven by a signal output from a voltage divider circuit 16000
to set the quiescent operating point of the detector 11000. The
base of the photo transistor 6000 is driven by a feedback signal,
to be described in more detail below, on line 16200 in order to
bias the photo transistor back to the optimum quiescent operating
point and, thus, account for the detection of ambient DC light. A
current mirror circuit 16400 supplies a fixed constant current to
the connected emitters of the photo transistor 6000 and the
transistor 15800 in the differential connection.
[0193] The photo transistor 6000 generates a first differential
output signal 11200 at its collector. The transistor 15800
generates a second differential output signal 11600 at its
collector. The first and second differential output signals 11200
and 11600 are one hundred eighty degrees out of phase with each
other and each have a peak to peak voltage that is representative
of detected light, including its color and shade, which is
reflected from the target surface. The second differential output
signal 11600 is applied to a buffer 11800 comprising a voltage
follower connected operational amplifier 16600. The signal 11600
output from the buffer 11800 is applied to the integrator 12000
which comprises an integrator connected operational amplifier
16800. The integrator 12000 makes a comparison of the buffered
signal 11600 to a DC reference voltage, and integrates the result
of that comparison to generate the feedback signal on line 16200
whose voltage is proportional to a detected error between the
desired quiescent operating point of the optical detector 11000 and
an average voltage shift therein caused by ambient (DC) light
detected by the photo transistor 6000, temperature variations in
the differential pair and other external factors, like component
aging. The generated feedback signal on line 16200 is then applied
to the base of the photo transistor 6000 to bias the component back
to the preferred quiescent operating point and thus account for
these external factors, in the peak to peak voltages of the
generated first and second differential output signals 11200 and
11600, which would otherwise result in measurement errors with
respect to the color and shade detection of the reflected pulsed
light emitted from the light source 10000.
[0194] The first and second differential output signals 11200 and
11600 are applied to the differential amplifier 11400 comprising a
differentially connected operational amplifier 17000. The
differential amplifier 11400 subtracts the first differential
output signal from the second differential output signal to provide
a single output signal 12200 on line 17200 having a peak to peak
voltage that is representative of detected light, including its
color and shade, which is reflected from the target surface. Any DC
components within this output signal 12200 are removed by a DC
blocking capacitor 17400. The remaining AC components, comprising
generally speaking a square wave whose peak to peak voltage is
proportional to the reflected light detected by the photo
transistor 6000 and representative of the color and shade
characteristics of that light, is then applied to the synchronous
detector 12400.
[0195] The synchronous detector 12400 receives the square wave
signal output from the square wave oscillator 10200 and uses it to
perform a synchronous full wave rectification of the output signal
12200 (demodulation) to produce a substantially steady DC voltage
indicative of the color or shade of color at the target surface.
This synchronous detection process further functions to eliminate
any shifts in the output signal 12200 caused by ambient (AC) light,
for example, from fluorescent light, detected by the photo
transistor 6000. More specifically, the synchronous detector 12400
functions to produce the substantially steady DC voltage which
accurately measures the peak to peak AC voltage of the output
signal 12200 derived from the optical detector without being
subject to any DC effects.
[0196] The synchronous detector 12400 includes an operational
amplifier 19200 that is selectively configured, based on the
received square wave signal, to provide for either inverting or
non-inverting unity gain processing of the output signal 12200.
This functionality is provided through the actions of a plurality
of CMOS switches. A first CMOS switch 18000 buffers and phase
inverts the square wave signal, and drives a second CMOS switch
18200 and a third CMOS switch 18400. The second CMOS switch 18200
functions as a phase inverter, such that the first and second CMOS
switches generate square wave output signals on line 18600 and
18800 that are one-hundred eighty degrees out of phase with each
other. One of those signals (line 18800) is applied to the third
CMOS switch 18400, and the other one of the signals (line 18600) is
applied to a fourth CMOS switch 19600. The third CMOS switch 18400,
when activated by the line 18800 signal, connects the non-inverting
input of the operational amplifier 19200 to a reference ground
supplied by diode 23800. The fourth CMOS switch 196000, when
activated by the line 18600 signal, connects the non-inverting
input of the operation amplifier 19200 to receive the DC blocked
output signal 12200. The output signal 12200 is further provided to
the inverting input of the operational amplifier 19200.
[0197] When the third CMOS switch 18400 is activated, the fourth
CMOS switch 19600 is not activated. Due to the grounding of the
non-inverting terminal, the operational amplifier 19200 is
configured to provide for unity gain inverted processing of the
output signal 12200. Conversely, when the third CMOS switch 18400
is activated, the fourth CMOS switch 19600 is not activated. Due to
the lifting of the ground and the connection of the output signal
12200 to the non-inverting and inverting terminals, the operational
amplifier 19200 is configured to provide for unity gain
non-inverted processing of the output signal 12200. By
appropriately phasing the square wave signal application to control
CMOS switch activation, a synchronous full wave rectification of
the output signal 12200 is provided.
[0198] Operation of the synchronous detector 12400 of the present
invention to provide for synchronous full wave rectification may be
better understood by reference to FIGS. 54A and 54B. In FIG. 54A,
there is shown the waveform 21000 for the output signal 12200 as
received by the synchronous detector 12400. The waveform 21000
includes a positive portion 21200 and a negative portion 21400 with
a peak to peak voltage that is indicative of the color or shade of
color at the target surface. Responsive to the square wave signal
(correctly phased), the third CMOS switch is activated to ground
the non-inverting terminal, and the operational amplifier 19200
thus is configured to provide non-inverting unity gain processing
of the output signal 12200 during the positive portion 21200. Next,
again responsive to the square wave signal (correctly phased), the
fourth CMOS switch is activated to connect the output signal 12200
to the non-inverting terminal and the operational amplifier 19200
thus is configured to provide inverting unity gain processing of
the output signal 12200 during the positive portion 21400. The
switching of the third and fourth CMOS switches continues as driven
by the square wave signal. The result of this selective processing
is to generate the output signal 12600 on line 20800, as shown in
FIG. 54B, having a substantially steady DC voltage indicative of
the color or shade of color at the target surface. The waveform
22000 includes a first portion 22200 corresponding to the
non-inverted (positive) portion 21200 of the output signal 12200,
and a second portion 22400 corresponding to the inverted (negative)
portion 21400 of the output signal 12200. It is noted that the
waveform 22000 still further includes a slight negative spike 21600
at each point where the output signal from the square wave
oscillator 10200 switches between low and high due to the CMOS
switch effects.
[0199] With reference now once again to FIGS. 53A and 53B, the
output signal 12600 on line 20800 is filtered by an R-C first order
low pass filter to remove the slight negative spikes 21600 within
the waveform 22000. The resulting filtered output signal 12600 is
then provided as a first analog signal output from the analog
portion of the reflectometer 3000/3000' for subsequent digital
processing, see FIGS. 52A and 52B).
[0200] The diode 23800 introduced DC level shift affects the DC
voltage level of the output signal 12600 from the synchronous
detector and, hence, the first analog signal output from the analog
portion of the reflectometer 3000/3000'. The DC level shift
therefore must be accounted for in order to ensure that the output
first analog signal is properly interpreted to detect color and
shade at the target surface. More specifically, the DC level shift
must be subtracted from the output signal 12600. Thus, the DC level
shift voltage is output on line 24000 as a second analog signal
output from the analog portion of the reflectometer 3000/3000' for
subsequent digital processing. This may be performed during digital
processing or, alternatively, taken care of in the analog portion
of the reflectometer 3000/3000' by utilizing a differential
amplifier (not shown) to perform the subtraction of the second
analog signal from the first analog signal prior to any subsequent
digital processing.
[0201] As discussed above, the reflectometer 3000/3000' further
includes a temperature sensor 12800. It is recognized that the LEDs
5000 are temperature sensitive components with respect to their
light output. In order to be able to accurately track operational
changes due to temperature variation, the temperature sensor 12800
preferably comprises a diode 23000, having operational
characteristics complementing those of the LEDs 5000,
thermo-mechanically coupled to the LEDs 5000 and electrically
connected between ground and the line 15200 square wave output from
the oscillator 10200 through a level adjustment circuit 23200
comprising a potentiometer 23400. This adjustment comprises a
factory performed adjustment to set a level for the temperature
indicative voltage output from node/line 23600. The temperature
indicative voltage on line 23600 thus comprises a third analog
signal output from the analog portion of the reflectometer
3000/3000' for subsequent digital processing.
[0202] Reference is now once again made to FIGS. 52A and 52B. The
first analog signal output, after subtracting the second analog
signal output, and the third analog signal output from the analog
portion of the reflectometer 30/30' are next digitally processed.
More specifically, the DC voltage of the first analog signal
representative of the detected reflected light at the target
surface, and indicative of color and shade, is analog-to-digital
converted to a first digital value. Similarly, the DC voltage of
the third analog signal representative of temperature is
analog-to-digital converted to a second digital value. The first
and second digital values are then processed to calculate a
compensated voltage that directly relates to the color and shade of
the non-spectral reflectance off the target surface at standard
conditions. The processor, by use of a stored lookup table that
correlates a certain compensated voltage, indicative of target
surface color and shade, to a certain analyte concentration, or
through the use of an appropriate mathematical formula, identifies
an analyte concentration level output value. The user selection of
reflectometer data, such as a manufacturing batch code for the
transdermal patch 1 or testing strip 2000, and type of testing to
be performed, for example, glucose versus cholesterol, identifies
which one of a plurality of stored lookup tables or formulae should
be considered by the processor in evaluating the compensated
voltage indicative of target surface color and shade to determine
the corresponding analyte concentration level output value.
[0203] As discussed briefly above, the intensity of the light
output from the LEDs 5000 is affected by ambient temperature. As
temperature increases, the intensity of the light output decreases.
Conversely, as temperature decreases, the intensity of the light
output increases. Accounting for any temperature changes at the
light source is thus imperative in order to ensure that the
detected steady DC voltage is an accurate representation of color
and shade.
[0204] A number of different temperature sensing mechanisms may be
utilized. In accordance with a first one of those mechanisms, it is
recognized that the LEDs 5000 are diodes, and that the diode 23000
may be advantageously used as a temperature sensor which mimics the
temperature sensitive operation of the LEDs. The voltage drop
across the diode is affected by temperature in the same way the
light intensity output from the LEDs 5000 is affected by
temperature. With a measurement of this voltage drop in comparison
to a reference voltage drop at a known temperature, it is possible
to determine current temperature.
[0205] As an example, the temperature dependance of the voltage
drop (V.sub.dC) of a small signal diode (such as 1N4148) is
measured to be approximately 0.0021 volts/degree C. At factory
calibration of the reflectometer 3000/3000', the forward voltage
drop across the diode 23000 is set by adjustment to the
potentiometer 23400 to, for example, 0.609 volts at twenty-five
.degree. C. Once this baseline voltage drop is established, any
measured difference between the actual voltage drop and the
baseline voltage drop can be easily converted into a temperature
variation, and that determined temperature variation accounted for
in evaluating both the operation of the LEDs 5000 and the first
analog output signal.
[0206] In this regard, it is noted that the temperature effect on
the light intensity output from the LEDs 5000 varies with the
detection signal nearly linearly over the limited temperature range
of interest with respect to the reflectometer 3000/3000'. A plot of
the temperature error in volts versus the reflectance, i.e., the
first analog signal representative of the detected reflected light
at the target surface and indicative of color and shade,
accordingly reveals a substantially straight line that intersects
the origin and has a positive slope of substantially 0.0035
volts/.degree. C. (hereinafter k1). The voltage adjustment
(.DELTA.V) that must be made to account for changes in temperature
from a standard may be calculated as follows:
.DELTA.V=k1.times.SV.times..DELTA.C [0207] wherein: SV is the
signal representative of the detected reflected light at the target
surface and indicative of color and shade; and [0208] .DELTA.C is
the sensed temperature change, i.e., detected offset, from a
reference standard of twenty-five .degree. C., and is equal to:
[0208] .DELTA. C = V dt - V dr V dC ##EQU00001## [0209] wherein:
V.sub.dt is the currently measured voltage drop across the diode;
and [0210] V.sub.dr is the voltage drop across the diode at a
reference standard of twenty-five .degree. C. The compensated
voltage CV, which accounts for the effects of temperature, may be
calculated through the use of standard mathematical manipulations,
the compensated voltage may be calculated as follows:
[0210] CV=SV.times.(1-k2.times.(V.sub.dt-V.sub.dC))
wherein: k2 is a constant equal to k1/V.sub.dC. In the case of the
specific example signal diode mentioned above, k2 equals
0.0035/0.0021=1.667.
[0211] Reference is now made to FIG. 55A wherein there is shown a
circuit diagram illustrating a second temperature sensing mechanism
useful in compensating for temperature. In this implementation,
direct first order compensation for the variations in light
intensity due to temperature is provided. One or two diodes 23000'
are connected in series with each other and the LEDs 5000 between
the square wave output on line 15200 and the light level adjustment
circuit 15400 comprising the potentiometer 15600. The diodes 23000'
are, like the diode 23000, thermo-mechanically coupled to the LEDs
5000. The voltage drop across the series connected diodes 23000'
with increased temperature results in the application of increased
current to the LEDs 5000. This increased current application
provides a first order compensation for any diminishment in light
intensity output from the LEDs 5000 due to increasing temperature.
For this series diode 23000' compensation scheme, it is preferable
to use a germanium or Schottky diode since the low forward voltage
drop of these types is an advantage in controlling the sensitivity
of the light-adjusting potentiometer 15600. This series diode
23000' compensation scheme may also be utilized in combination with
the diode 23000 sensor configuration illustrated in FIGS. 53A and
53B to provide for improved temperature detection and
compensation.
[0212] Reference is now made to FIG. 55B wherein there is shown a
circuit diagram illustrating a third temperature sensing mechanism
useful in compensating for temperature. In this implementation, a
measurement of voltage drop is taken across one of the LEDs 5000,
across each of the LEDs, or across all of the LEDs. Using this
measured instantaneous LED voltage drop, dynamic temperature
compensation may be implemented to account for not only currently
experienced temperature variations, but also long term degradation
of the LEDs 5000. In connection with the reflectometer 3000/3000'
illustrated in FIG. 52A, a voltage drop detector 25200 is provided
to measure the voltage drop across one, each or all of the LEDs
5000. The measured voltage drop may then be output through the
external port connection for processing by the personal computer in
accordance with the CV equation discussed above. In connection with
the reflectometer 3000/3000' illustrated in FIG. 52B, on the other
hand, a pair of analog taps 25400 are taken off the anode/cathode
leads of one, each or all of the LEDs 5000 and input to the
microprocessor. The analog to digital converter of the
microprocessor then converts the measured voltages to digital
signals, subtracts the values from each other and determines a
resulting voltage drop for subsequent processing in accordance with
the CV equation discussed above.
[0213] With reference now once again to FIGS. 53A and 53B, a fourth
temperature sensing mechanism useful in compensating for
temperature advantageously utilizes the synchronous detector DC
level shifting diode 23800 to measure temperature by sensing the
voltage drop across the diode. In one configuration, the diode
23800 may be thermo-mechanically coupled to the LEDs 5000 to
provide light source related temperature information for subsequent
processing in accordance with the CV equation discussed above. In
another configuration, the diode 23800 may remotely located from
any heat sources within the reflectometer 3000/3000' in order to
provide ambient temperature information for subsequent processing
in connection with evaluations which are dependent on knowing
ambient, as opposed to light source temperature. As an example, the
biological and chemical reactions on the transdermal patch and/or
strip are ambient temperature dependent. In order to calculate
accurate incubation times, the diode 238 ambient temperature data
may be processed to identify when is the proper time to take a
reading.
[0214] Reference is now once again made to FIGS. 48A, 48B and 49.
As discussed above, the reflectometer 3000/3000' is minimally
affected by the external influence of light, induced noise, and
temperature. Accordingly, the cylindrical shaped protruding nose
4800 portion of the sensor head 3200 need not necessarily provide a
light-tight fit with the opening 33 in the transdermal patch 1
because leakage of ambient light, just like skin color, is
compensated for by the synchronous detection feature. Internally,
the alternating nature of the light source and detector circuit is
not subject to DC drift. Furthermore, temperature compensation
concerns have also been addressed through the use of temperature
detection and compensation circuitry and processing as discussed
above.
[0215] There are, however, other factors that can effect the
accuracy of the color and shade reading. For example, the unsteady
operation of the reflectometer 3000 due, for example, to a rocking
motion or other movement, may alter the illumination geometry at
interface between the sensor head 3200 and the transdermal patch 1.
Another concern is the application of varying degrees of contact
pressure between the reflectometer 3000 and the transdermal patch
1. With specific respect to a hand-held device, it is vitally
important that the routine to measure a repeatable peak hold on the
output signal indicative of detected color and shade must be
tolerant of vibrations and unsteady operation. To achieve this
goal, data is sampled at a high enough rate such that as many data
points as practical are input into an averaging routine. The
technique for averaging these samples should be able to determine
the correct reading within a few seconds and not be affected
however by the time to take a reading.
[0216] Peak detection voltage stability is utilized as the test for
insuring a repeatable result. If, for example, the detection
voltage range is between 0.5 and 0.8 volts, then a peak detection
voltage stability of 0.002 volts would provide for better than one
percent resolution. A signal gain of five would result in a range
of two and half to four volts, a range that is more compatible with
a microprocessor having an analog to digital converter with a five
volt supply.
[0217] Reference is now made to FIGS. 56 and 59 wherein there is
shown an exemplary operation of the peak hold detection algorithm
used in processing the DC voltage of the first analog signal
representative of the detected reflected light at the target
surface, and indicative of color and shade.
[0218] Raw data relating to un-compensated voltage is collected at
a certain sampling rate (step 50000). A moving block average
(Av(i)) is then calculated for the last n samples (step 50200). The
moving block average Av(i) is then compared in step 50400 to the
most recent previous moving block average (Av(i-1)). If the
deviation between the current moving block average Av(i) is less
than a certain deviation voltage threshold from the most recent
previous moving block average Av(i-1), then a steady state
condition has been satisfied, and the current moving block average
Av(i) is held as a peak value in step 506oo for subsequent
processing as the steady DC voltage indicative of the color and
shade of the target surface. If the step 50400 measured deviation
exceeds the certain deviation voltage threshold, the process
returns to step 50200 to calculate a new current moving block
average. The process continues sampling (step 50000), calculating
moving block averages (step 50200), and comparing (step 50400)
until the determined deviation between the current moving block
average Av(i) and the most recent previous moving block average
Av(i-1) is less than a certain deviation voltage threshold.
[0219] The held peak value for the steady DC voltage is then
processed first to adjust for the DC offset, then to correct for
temperature, and then to adjust for color and/or batch calibration,
if desired or necessary. The resulting compensated voltage directly
relates to the color and shade of the reflectance off the target
surface at standard conditions. The processor, by use of a stored
lookup table or mathematical formula, based perhaps upon lookup
table related data, that correlates a certain compensated voltage,
indicative of target surface color and shade, to a certain analyte
concentration, identifies an analyte concentration level output
value. If the compensated voltage value falls between two rows in
the lookup table, the end data points for the analyte concentration
level are interpolated to produce an output. The user selection of
reflectometer data, such as a manufacturing batch code for the
transdermal patch 1 or testing strip 2000, and type testing to be
performed, for example, glucose versus cholesterol, identifies
which one of a plurality of stored lookup tables should be
considered by the processor in evaluating the compensated voltage
indicative of target surface color and shade to determine the
corresponding analyte concentration level output value. Other
factors that may affect the calibration to an individual can also
be affected by the choice of the lookup table. An example of a
lookup table suitable for use in the reflectometer of the present
invention is illustrated in FIG. 57.
[0220] In the context of the lookup table of FIG. 57, or its
equivalent mathematical formula, an example of the use of the
reflectometer 3000/3000' to monitor glucose level is now presented.
At 10:00 am, a pre-set audible alarm alerts the diabetic patient to
take a glucose reading. A transdermal patch 1 is attached to the
inside of the patient's forearm and the SELECT button is pressed,
signaling the beginning of an incubation countdown period. After
the period expires, another audible alarm having a distinct tone
sequence alerts the patient that it is time to take a reading on
the patch 1. The cylindrical shaped protruding nose 4800 portion of
the sensor head 3200 is inserted within the opening 33 in the
transdermal patch 1, and the READ button is pushed. After about one
second of reading time, the first analog output signal has not yet
reached a steady state condition, relative to the certain deviation
voltage threshold. After about two seconds, steady state is reached
and a DC offset adjusted, but temperature un-compensated, voltage
is obtained with a value of 0.664 volts. This steady DC voltage is
then presented to the processor as the first analog output signal
for analysis. In addition, the temperature sensor diode 23000
provides the third analog output signal with a value of 0.611
volts. In accordance with the temperature correction algorithm
described above, a compensated voltage CV indicative of target
surface color and shade is then calculated at 0.662 volts. If
necessary, appropriate color and/or batch calibration adjustment
may also be made. In the lookup table of FIG. 57, or its equivalent
mathematical formula, this compensated voltage correlates with a
glucose level of between 14000 and 180 mg/dL. Interpolation of
these two end points produces a final result of 170.4 mg/dL. This
glucose level is then rounded to the nearest whole number, and a
final result of 170 mg/dL is displayed to the patient. The result
is also stored in memory along with the date and time for future
reference or to be downloaded to a computer as patient history.
[0221] Reference is now made to FIG. 58A wherein there is shown a
cross-sectional view illustrating an improper engagement of the
reflectometer and the transdermal patch. As mentioned previously,
one of the factors that can affect the accuracy of the color and
shade reading is the application of varying degrees of contact
pressure between the reflectometer 3000 and the transdermal patch
1. In this regard, it is noted that accurate measurement is
dependent upon the target surface being in proper position. Uneven
or excessive pressure can, however, distort, i.e., bow or ripple,
the membrane 20 and move the target surface out of proper position.
This effect is shown in exaggerated fashion in FIG. 58A. It has
been observed that the result of increasing pressure applied to the
patch by the reflectometer meter causes an increased reflectance
signal due to the target surface deflecting toward the photo
transistor. Furthermore, in some instances the membrane is
inherently distorted or is distorted as a result of the biological
and chemical reaction.
[0222] Reference is now made to FIG. 58B wherein there is shown a
cross-sectional view illustrating the use of a window 29000 on the
cylindrical shaped protruding nose 4800 portion of the
reflectometer sensor head 3200. The window 29000 serves to flatten
out any existing distortions, bows, ripples and the like, in the
membrane 20 and further render the measurement process relatively
insensitive to variations in applied pressure. The target surface
is accordingly accurately positioned for color and shade reading.
The window 29000 is transparent and is preferably made of a plastic
or glass that exhibits a high transmissivity at the wavelength of
the light source light used, in this case, that wavelength emitted
by the LEDs 5000. Additional requirements include durability and
resistance to cleaning solutions and scratching. As an added
benefit, the clear window 29000 prevents dirt, dust and debris,
which could reduce the sensitivity of the reflectometer and might
also affect the calibration, from entering and accumulating within
the sensor head.
[0223] Reference is now made to FIG. 58C wherein there is shown a
cross-sectional view illustrating the use of a tapered cylindrical
shaped nose portion 4800' of the reflectometer sensor head 3200. As
discussed above, the reflectometer 3000/3000' is substantially
immune to the external influence of light. Accordingly, the nose
portion 4800/4800' of the sensor head 3200 need not necessarily
provide a light-tight fit within the opening 33 in the transdermal
patch 1. Leakage of ambient light, just like skin color, is
compensated for by the included feedback signal and synchronous
detection features. However, it is important, as illustrated in
FIG. 58A, that the target surface be placed in proper position with
respect to the head 4800/4800'. A cylindrical shaped sensor head
4800, like that shown in FIGS. 49, 58A and 58B, having a diameter
nearly identical to the diameter of the circular opening in the
transdermal patch 1 may not, in instances where the user is not
careful, seat itself properly within the opening flush against the
membrane. As an additional concern, the top surface of the
transdermal patch may have an adhesive layer that could catch the
nose making it more difficult to properly seat the nose within the
patch opening. To assist the user in obtaining proper flush
positioning of the reflectometer 3000, the tapered shape of the
cylindrical shaped nose portion 4800' of the reflectometer sensor
head 3200 functions to find the opening in the patch 1 during
insertion and facilitate proper placement of the reflectometer
against the membrane. The window 29000 is preferably recessed into
the nose by its thickness to seal the opening in the sensor head
and prevent the edge of the window from being caught and possibly
damaged or removed during handling.
[0224] Reference is now once again made to FIGS. 52A and 52B. As
mentioned previously, the reading process is initiated by having
the user depress the SELECT button. This button signals the
beginning of an incubation countdown period. It is recognized that
the time required for completion of the biological and chemical
processes that occur on the patch 1 or strip 2000 may be
temperature dependent. Thus, the processor of the reflectometer
3000/3000' utilizes the diode 23800 to obtain information
indicative of ambient temperature. When the SELECT button is
activated, the processor uses the current ambient temperature
information provided by the diode 23800 to determine an incubation
countdown period of sufficient length to insure completion of the
biological and chemical processes on the patch 1 or strip 2000
before signaling the user with an audible alarm indicating that it
is time to take a reading.
[0225] Reference is now made to FIGS. 53A and 53B and to FIG. 60
wherein there is shown a flow diagram illustrating a process for
performing a first order calibration of the reflectometer
3000/3000'. It is noted that this first order calibration must be
performed at a controlled temperature, such as twenty-five .degree.
C. A point on the compensated voltage-analyte concentration curve,
such as that represented by the lookup table of FIG. 57, is chosen
in step 35000 where it is preferred that the reflectometer be able
to read most accurately. In most instances this point will be at or
close to midrange on the curve. The reflectometer 3000/3000' is
then exposed in step 35200 to a standard color shade that
corresponds with that chosen analyte concentration. A resulting
compensated voltage or analyte concentration values is then output
in step 35400. The internal potentiometer 15600 of the light level
adjustment circuit 15400 is then adjusted in step 35600, with an
adjusted compensated voltage being output in step 35800. A test is
then made in step 36000 to determine whether the step 35600
adjustment produced an adjusted compensated voltage in step 35800
that matches the step 35000 selected point on the compensated
voltage-analyte concentration curve. If not, the process returns to
perform steps 35600, 35800 and 36000 over again. This is repeated
until such time as the potentiometer 15600 adjustment produces an
adjusted compensated voltage that matches the compensated voltage
at the selected point on the compensated voltage-analyte
concentration curve. If this first order calibration process is
performed with respect to each reflectometer 3000/3000', then each
reflectometer will read exactly the same way at the midpoint, thus
providing consistency in reflectometer operation from device to
device.
[0226] Reference is now made to FIGS. 52A and 52B and to FIG. 61
wherein there is shown a flow diagram illustrating a process for
performing a second order calibration of the reflectometer
30001/3000'. It is noted that this second order calibration must be
performed at a controlled temperature, such as twenty-five .degree.
C. A point on one end of the compensated voltage-analyte
concentration curve, such as that represented by the lookup table
of FIG. 57, is chosen in step 37000. The reflectometer 3000/30' is
then exposed in step 37200 to a standard color shade that
corresponds with that chosen analyte concentration. A resulting
compensated voltage value is then output in step 37400. A first end
point offset between the output compensated voltage value and the
compensated voltage at the selected end point on the compensated
voltage-analyte concentration curve is then determined in step
37600 and stored, in non-volatile memory, by the processor in step
37800. At this point, a measurement is also made of the voltage
drop across the temperature sensor 12800 diode 23000 and stored, in
non-volatile memory, by the processor in step 36200. A point on the
other end of the compensated voltage-analyte concentration curve is
then chosen in step 38000. The reflectometer 3000/3000' is then
exposed in step 38200 to a standard color shade that corresponds
with that chosen analyte concentration. A resulting compensated
voltage value is then output in step 38400. A second end point
offset between the output compensated voltage value and the
compensated voltage at the selected end point on the compensated
voltage-analyte concentration curve is then determined in step
38600 and stored, in non-volatile memory, by the processor in step
38800. A point in the middle of the compensated voltage-analyte
concentration curve is then chosen in step 39000. The reflectometer
3000/3000' is then exposed in step 39200 to a standard color shade
that corresponds with that chosen analyte concentration. A
resulting compensated voltage value is then output in step 39400. A
mid-point offset between the output compensated voltage value and
the compensated voltage at the selected end point on the
compensated voltage-analyte concentration curve is then determined
in step 39600 and stored, in non-volatile memory, by the processor
in step 39800. The stored first and second end point offsets and
mid-point offset may then be taken into account by the processor in
using the stored lookup table, or mathematical algorithm, which
correlates a certain compensated voltage, indicative of read target
surface color and shade, to a certain analyte concentration, to
identify an analyte concentration level output value. Although not
specifically illustrated, more than two or three points on the
curve may be selected for second order calibration in order to
provide for more accurate operation.
[0227] It is noted that the second order calibration process of
FIG. 61 may be performed multiple times on a single meter in
situations where the meter is likely be utilized to make readings
for different types of tests, for example, glucose and cholesterol.
In such a case, the reflectometer 3000/3000' is programmed with
plural stored lookup tables, or mathematical algorithms, which each
correlate a certain compensated voltage, indicative of read target
surface color and shade, to a certain analyte concentration. The
reflectometer must be calibrated to applicable data for each of
those tests in order to ensure proper performance.
[0228] It is recognized that the color indications developed on the
transdermal patches or strips may vary between manufacturing
batches. One way to handle this concern is to code each batch in
accordance with its color indications. Each meter is then
preprogrammed with the batch code designations and appropriate
offsets at the first and second end points and mid-point. In
situations where preprogramming in this manner is not possible, the
process illustrated in FIG. 61 may be performed by the patient, as
opposed to at the factory, with respect to each batch of
transdermal patches or strips used. To support this patient batch
code (third order) calibration process, each batch of transdermal
patches or strips would include three standard color shades, with
each shade corresponding with a certain analyte concentration as
measured by that batch. After completion of the process, stored
first and second end point offsets and mid-point offset relating to
batch variation may then be taken into account by the processor in
using the stored lookup table, or mathematical algorithm, which
correlates a certain compensated voltage, indicative of read target
surface color and shade, to a certain analyte concentration, to
identify an analyte concentration level output value.
[0229] Reference is now made to FIG. 57 and to FIG. 62 wherein
there is shown a graph illustrating an exemplary compensated
voltage-analyte concentration curve 40000 and the affect thereon of
the first and second order calibration processes of FIGS. 60 and
61, respectively. The curve 40000 represents the relationship
between a certain measured compensated voltage, on the y-axis, and
a corresponding analyte concentration, on the x-axis. More
precisely, the curve 40000 presents the specific compensated
voltage-analyte concentration relationship illustrated in FIG.
57.
[0230] Turning first to the first order calibration process of FIG.
60, a mid-point 40200 on the curve 40000 of FIG. 62 is selected, in
this instance representing an analyte concentration of 30000 mg/dL.
The reflectometer is then exposed to a standard color shade that
corresponds with that chosen analyte concentration. Instead of
producing a corresponding expected compensated voltage 40400
reading (in this instance comprising 550 mV), the reflectometer
reports a different compensated voltage 40600. Appropriate
potentiometer 15600 adjustment is then performed in order to bring
the reflectometer reported compensated voltage 40600 into a
matching relationship with the expected compensated voltage 40400.
Storage is also made at this point of the voltage drop across the
temperature sensor 12800 diode 23000.
[0231] Turning next to the second order calibration process of FIG.
61, a first end point 40800 on the curve 40000 of FIG. 62 is
selected, in this instance representing an analyte concentration of
625 mg/dL. The reflectometer is then exposed to a standard color
shade that corresponds with that chosen analyte concentration.
Instead of producing a corresponding expected compensated voltage
41000 reading, in this instance comprising 400 mV, the
reflectometer reports a different compensated voltage 41200. The
offset d1 between the expected compensated voltage 41000 and the
reflectometer reported compensated voltage 41200 is determined and
stored. A second end point 41400 on the curve 40000 is selected, in
this instance representing an analyte concentration of 55 mg/dL.
The reflectometer is then exposed to a standard color shade that
corresponds with that chosen analyte concentration. Instead of
producing a corresponding expected compensated voltage 41600
reading, in this instance comprising 850 mV, the reflectometer
reports a different compensated voltage 41800. The offset d2
between the expected compensated voltage 41600 and the
reflectometer reported compensated voltage 41800 is determined and
stored. A mid-point 42000 on the curve 40000 is selected, in this
instance representing an analyte concentration of 300 mg/dL. The
reflectometer is then exposed to a standard color shade that
corresponds with that chosen analyte concentration. Due to the
first order calibration provided above, the reflectometer should
produce the expected compensated voltage 40400 reading, in this
instance comprising 550 mV. If it does not, then the first and
second order calibration processes should be performed again. In
the event the reflectometer is being programmed for use in
connection with different types of tests, for example, glucose and
cholesterol, the reflectometer likely will not produce the expected
compensated voltage 40400 reading. Rather, the reflectometer
reports a different compensated voltage 40600. The offset d3
between the expected compensated voltage 40400 and the
reflectometer reported compensated voltage 40600 is determined and
stored. The stored first and second end point offsets d1 and d2 and
mid-point offset d3 may then be taken into account by the processor
in using the stored lookup table, see FIG. 57, or mathematical
formula when processing a detected compensated voltage, indicative
of read target surface color and shade, to identify an analyte
concentration level output value. The result of this second order
calibration is, in effect, to produce an adjusted compensated
voltage-analyte concentration curve 40000', illustrated with a
dashed line, for each type of test that takes into account the
tolerances of the specific reflectometer 3000/3000' at issue. In
processing the reflectometer 3000/3000' detected compensated
voltage at points on the curve 40000, look-up table of FIG. 57,
between the end-points 40800 and 41400, an interpolation of the
appropriate d1, d2 or d3 offset may be calculated, along with any
interpolation necessary to make the calculation between the data
points in the look-up table or mathematical formula, making a final
determination of an analyte concentration level output value. The
foregoing process may then be repeated by the patient in order to
calculate additional d1, d2 and d3 offsets and thus produce another
adjusted compensated voltage-analyte concentration curve 39000',
illustrated with a dashed line, for each batch of patches or
strips.
[0232] Reference is now made to FIG. 63 wherein there is shown a
flow diagram illustrating a process for converting an input voltage
indicative of read color shade into a concentration value output.
The illustrated process not only accounts for any temperature
considerations in generating the compensated voltage, but also
accounts for any interpolations required by the second order
calibration offsets, see FIG. 61, and the calculation between the
data points in the look-up table, see FIG. 57. In step 60000, a
stable output voltage indicative of color and shade has been
determined, see FIG. 59. If any DC offsets affecting the accuracy
of stable output voltage are present, such as that provided with
respect to the synchronous detector, these offset(s) are subtracted
from the stable output voltage in step 60200. Next, in step 60400,
the offset adjusted stable output voltage is processed using the
equation discussed above to compensate for variations in light
source intensity due to temperature and produce a compensated
voltage (CV). The compensated voltage is then processed in step
60600 to make any needed adjustments relating to second order color
calibration and third order batch code calibration, see FIGS. 61
and 62. A lookup table (or mathematical formula) is then used to
convert the color (batch code) calibration adjusted compensated
voltage in step 60800 to a concentration level. Any necessary
interpolations to the determined concentration level are then made
in step 61000. A determination is then made in step 61200 as to
whether the (interpolated) determined concentration level is within
an acceptable anticipated range for the particular test being made.
If not, an error message is displayed in step 61400, and record of
the error is stored in step 61600 along with a date and time of
day. If so, the (interpolated) determined concentration level is
displayed in step 61800, and record of the level is stored in step
61600 along with a date and time of day.
[0233] Examples of varies embodiments of the present invention will
now be further illustrated with reference to the following
examples.
[0234] Unless otherwise stated in a specific example, the targeted
skin area and the dry chemistry membranes in the following Examples
are treated and prepared, respectively, as follows.
[0235] To make a dry glucose chemistry membrane, a 100 ml base
preparation is first prepared. This base preparation contains:
[0236] about 60 .mu.m Polyvinyl pyrrolidinone K-30 (mw 40,000)
[0237] about 1.2 gm Citric Acid Trisodium Salt
[0238] about 0.1 gm Citric Acid Monohydrate
[0239] about 0.028 gm NaBH.sub.4 (sodium Borohidrate)
[0240] about 0.1 gm Bovine Serum Albumin (BSA)
[0241] The ingredients for the base solutions are dissolved and
thoroughly mixed. Once the base solution is prepared, the following
quantities of conditioning, flow and stabilizing agents and
indicators are added:
[0242] about 0.546 gm O-Tolidine [0243] adjust pH to about 5.9 to
about 6.0
[0244] about 2.0 ml 10% Ganttrez S-95 (10.0 gm/100 ml) is added and
pH is adjusted to [0245] about 5.9 to about 6.0 with NaOH.
[0246] about 4.0 gm/L 75% DOSS [0.533 gm].
[0247] The conditioning flow agents, stabilizing agent (BSA) and
the indicator (O-Tolidine) is dissolved and mixed well into the
base preparation. Once the agents and indicator are blended
intimately into the base preparation, the specific enzymes for
reaction with glucose are added:
[0248] about 121.0 mg Glucose Oxidase (60D) 150 u/ml [0249]
[150u*100 ml/124 u/mg]
[0250] about 38.53 mg Horse Radish Peroxidase (POD) 100 u/ml [0251]
[100u*100 ml/259.55 u/mg].
[0252] The enzymes are added and stirred thoroughly.
[0253] To prepare a membrane, a Biodyne A membrane (0.45 micron
pore size) is dipped briefly for about 30 seconds into the prepared
enzymatic cocktail until uniformly wetted. It is then air dried at
about 37.degree. C. for about 15 minutes. The dried membrane is
stored with desiccant protected from moisture and light. The dried
glucose chemistry membrane can be cut into strips of a size about
0.75 inches with an exposed testing area of about 3/16 inches, and
the cut strips can be encapsulated or glued within the fold of an
adhesive coated mylar, such as Dermaflex PM 500 within a patch
configuration, such as illustrated in FIG. 3. It is believed that
approximately 5 liters of the enzymatic cocktail will effectively
treat 200 sq. ft. of the Biodyne A membrane.
[0254] Before conducting the experiments, the targeted skin area
and the hands of the user are treated as follows unless specified
otherwise.
[0255] First, user cleans his/her hands and the targeted skin area
thoroughly with deionized water (18 meg ohm). The targeted skin
area and hands may be rinsed with the deionized water or wiped with
a non-bleached paper towel that has been wetted with the deionized
water. The cleansed skin area and hands are then dried with a
non-bleached paper towel. Users should avoid the use of bleached
paper towels and chlorinated water.
[0256] If the targeted skin area is to be pretreated with a skin
permeation enhancer, the cleansed and dry targeted skin area is
then wiped one or more times with a KimWipe.RTM. which is wetted
with about 0.5 ml of a selected permeation enhancer. A suitable
size KimWipe.RTM. for application of the 0.5 ml skin permeation
enhancer is dimensioned at 5.times.5 cm. While KimWipes.RTM. are
used, any other ultra clean, lint-free, non-bleached paper towels
may be used. KimWipes.RTM. are supplied by Kimberly Clarke.
[0257] Once the precleansed targeted skin area is treated with a
skin permeation enhancer, the pretreated skin is inspected to
ensure that there is not excessive skin permeation enhancers on the
skin. If too much has been applied, the patch adhesive may not
stick. Thus, any excess skin permeation enhancer should first be
removed with, for example, a KimWipe.RTM., before applying the
patch.
[0258] If an organic solvent type skin permeation enhancer is
selected, such as isopropyl alcohol or ethyl acetate, it is
preferable to allow the organic solvent to first dry or evaporate
before applying the patch to the treated skin area to avoid
potential negative interaction between the organic solvent type
skin permeation enhancer and the chemical reagents on the membrane.
If the skin permeation enhancer selected is not an organic solvent,
the patch may be applied immediately following treatment of the
skin area with such skin permeation enhancer.
[0259] Before the patch is applied, it is removed from its foil
envelopes with 1 gram of desiccant. Following removal, the selected
transfer medium or gel is loaded into the hole in the bottom of the
patch to uniformly and continuously wet the membrane. Once the
membrane is wetted with the gel, the test should be conducted
within 5 to 10 minutes thereafter. Also, wetted membrane should not
be exposed to bright lights.
[0260] Once the patch is positioned on the targeted skin area, it
is left therefor about 5 minutes, at which time the color change is
read by a reflectometer to detect the present of glucose.
[0261] Also, unless otherwise specified, the wet chemistry gel
utilized is about 1% carboxy methylcelluose in deionozed water (18
meg ohm).
Example 1
[0262] The following two figures represent data obtained with a
glucose patch in accordance with the present invention. The glucose
membrane is prepared similar to that described immediately
above.
[0263] FIG. 11 shows results of a glucose tolerance test performed
on a non-diabetic subject over a three hour period. These results
in FIG. 11 show a high correlation between the glucose patch and a
current popular finger stick method. In this example, the wipe is
propylene glycol.
Example 2
[0264] FIG. 12 shows the results of a series of tests that are
performed on a Type I insulin dependent diabetic over a 21 day
period. One sample is taken per day in a random manner--with no
control over the sampling time of day or relation to the patient's
insulin.
Example 3
[0265] FIG. 13 depicts data from a series of experiments testing
the linearity of the glucose patch reaction chemistry to increasing
concentrations of glucose. Four glucose determinations are
performed daily on a series of standards and the results correlated
after four days of tests. These results show that the detection
membrane is capable of measuring the minute amounts of glucose.
[0266] FIG. 14 depicts an actual calibration curve for the glucose
patch. The data is depicted in FIG. 15A. A set of these glucose
patches are evaluated with calibration standards using nine patches
for each standard. The coefficient of variation averaged less than
4% with an r-value of 0.99 for the standard curve after 5 minutes
of reaction time.
Example 4
[0267] The following is data resulting from oral glucose tolerance
tests of volunteers. The tests are designed to compare the results
obtained with the glucose patch to a "state of the art" capillary
blood glucose method from other companies. The patch reflectance
data is obtained using a reflectometer as described herein. These
people have not eaten for twelve hours prior to the tests. After
initial glucose determinations, they drank a solution of 100 grams
of glucose within five minutes. The comparative tests are continued
over the course of 1.5-3 hours. Note that the capillary blood
glucose values rise to a peak level by 30-50 minutes and then
return to "normal", as is expected with nondiabetics. The patch
reflectance values parallel the capillary blood glucose values and
are much easier to obtain.
[0268] All blood results are obtained using an FDA "accepted"
standard finger stick capillary blood glucose method with the
manufacturers electronic meter indicated for each test and strips
by the recommended procedure.
[0269] Patient 1 is a normal person (older Caucasian male) who is
tested at fasting level through postprandial 100 grams glucose for
three hours:
TABLE-US-00004 Blood Glucose Time (min.) Life Scan II Patch Glucose
Postprandial mg/dl mg/dl 0 78 80 15 94 78 25 120 130 32 117 110 68
92 95 110 92 95 150 76 75 180 73 85
[0270] Patient 2 is a normal (older Caucasian male) person who is
tested at fasting level through postprandial 100 grams glucose for
three hours:
TABLE-US-00005 Blood Glucose Time (min.) Life Scan II Patch Glucose
Postprandial mg/dl mg/dl 0 73 92 15 91 99 50 128 125 90 99 98 120
95 95 180 75 60
[0271] Patient 3 is a normal person (young Caucasian female) who is
tested after breakfast through lunch, moderate exercise, and a
snack, for three hours:
TABLE-US-00006 Blood Glucose Time (min.) Life Scan II Patch Glucose
Postprandial mg/dl mg/dl 0 77 120 24 130 136 90 111 106 120 113 113
180 143 102
[0272] Patient 4 is a normal person (young African American male)
who is tested fasted for two hours:
TABLE-US-00007 Blood Glucose Time (min.) Life Scan II Patch Glucose
Postprandial mg/dl mg/dl 0 55 81 30 103 108 60 90 85 120 98 88
[0273] Patient 5 is a type I diabetic patient (older Caucasian
male) who is tested on twenty two occasions by several different
extraction formulations:
TABLE-US-00008 Blood Glucose Time (min.) Life Scan II Patch Glucose
Postprandial mg/dl mg/dl 1 268 247 2 196 157 3 109 110 4 108 101 5
314 265 6 207 251 7 140 106 8 267 203 9 367 248 10 267 256 11 267
228 12 267 251 13 267 218 14 227 190 15 216 196 16 213 200 17 222
180 18 214 181 19 183 127 20 179 130 21 180 127 22 178 125
[0274] Patient 6 is a normal person (young African American male)
who is tested over the course of two hours:
TABLE-US-00009 Blood Glucose Time (min.) Life Scan II Patch Glucose
Postprandial mg/dl mg/dl 0 132 116 30 113 110 60 115 120 90 144 142
120 116 118
[0275] Patient 7 is a normal person (young Caucasian female) who is
tested after breakfast through lunch, moderate exercise, and a
snack, for two and 1/2 hours:
TABLE-US-00010 Blood Glucose Time (min.) Life Scan II Patch Glucose
Postprandial mg/dl mg/dl 0 111 120 30 237 160 60 167 98 90 121 125
120 173 140 150 180 165
[0276] Patient 8 is a normal person (older Caucasian male) who is
tested after fasting level through postprandial 100 grams glucose
for two hours:
TABLE-US-00011 Blood Glucose Time (min.) Life Scan II Patch Glucose
Postprandial mg/dl mg/dl 0 95 70 15 113 104 25 120 122 40 83 78 50
90 86 75 92 75 110 79 69
[0277] Patient 9 is a normal person (young Asian female) who is
tested after breakfast through lunch, and a snack, for two
hours:
TABLE-US-00012 Blood Glucose Time (min.) Life Scan II Patch Glucose
Postprandial mg/dl mg/dl 0 141 120 30 91 110 60 97 100 90 144 126
120 233 165
[0278] Patient 10 is a normal person (young Caucasian male) who is
tested after breakfast then glucose load for two hours:
TABLE-US-00013 Blood Glucose Time (min.) Life Scan II Patch Glucose
Postprandial mg/dl mg/dl 0 89 105 30 125 123 60 97 105 120 105 120
PATIENT KEYS N = Normal D = DIABETIC TYPE I; O = OLDER =MIDDLE AGE
(NONE TESTED) Y = YOUNGER C = CAUCASIAN A = AFRICAN AMERICAN AS =
ASIAN M = MALE F = FEMALE
[0279] The results of the comparison of a standard finger stick
method with glucose patch subjects undergoing glucose tolerance
tests are depicted in FIGS. 16, 17 and 18. One type I diabetic
subject (#5) is included. For comparison, two different "NO WIPE"
finger stick method are also used. Subject #9 (see FIG. 11) engages
in some extensive manual labor between testing, and as depicted,
despite the glucose load she receives, her glucose level decreases.
She also begins the glucose tolerance test late and eats lunch
before the end of the test period.
[0280] Subject 5 (See FIG. 18, top graph) is a diabetic subject who
subsequently performs 22 assays at various skin sites. Instead of
receiving a glucose load as with the other 9 patients, this
diabetic delays insulin administration then tests both before and
after insulin for two separate, four test periods. Comparison #8-22
in FIG. 18, top graph, reflect one series of tests a day consisting
of 6 simultaneous patches using different skin sites, which are
performed before administering insulin, and which are followed by 5
simultaneous patches on the same sites which are performed later in
the day after eating, but before diabetic's injection and finally 4
simultaneous patches at different sites after giving sufficient
time for the insulin to lower the diabetic's glucose levels.
Example 5
[0281] FIG. 19 illustrates the results of the comparison of blood
glucose levels in eight (8) non-diabetics using patches vs. finger
stick. It confirms that the correlation between finger stick tests
and plasma glucose in the range of from r.sup.2=0.53-0.93 comparing
different finger stick tests using both name brand and generic
strips.
Example 6
[0282] A similar series of experiments are performed with a
diabetic subject. See FIG. 20. FIG. 20 shows that the patch and
finger stick blood glucose levels correlate in a highly significant
fashion with a coefficient of determination r.sup.2=0.791 and
significant level of p=0.001. These results are obtained on one
subject over several months. This data demonstrates good
correlation over a glucose range of 100-300 mg/dl. There are no
changes in diabetic therapy or insulin dosages throughout the
testing period. One portion of the diabetic data defines the
variance as a single subject with three patches on each arm.
Example 7
[0283] Two individuals, MM and JM, volunteered to test 5 different
gels and 6 different wipes in combination with a super sensitive or
conditioned glucose membrane in accordance with the present
invention.
[0284] Prototype glucose membranes are made as described earlier
herein with respect to the alternative glucose reactive
membrane.
[0285] The glucose patch, into which the glucose membrane was
placed, is similar to the patch depicted in FIG. 3.
Gels
[0286] The five gels are as follows:
1. About 1% carbopol in deionized water; 2. About 10% glycerin and
about 1% carbopol in deionized water; 3. About 10% polyethylene
glycol and about 1% carbopol in deionized water; 4. About 10%
propylene glycol and about 1% carbopol in deionized water 5. About
10% sodium lauryl sulfate and about 1% carbopol.
[0287] The gels are made by simply mixing the components together
thoroughly as described herein.
Wipes
[0288] The six wipes are as follows:
1. About 10% glycerin in deionized water; 2. About 10% polyethylene
glycol in deionized water (18 meg ohm); 3. About 10% propylene
glycol in deionized water (18 meg ohm); 4. About 10% sodium lauryl
sulfate in deionized water (18 meg ohm); 5. 1:1:1 ethyl
alcohol:isopropyl alcohol:deionized water 6. 1:1:1 ethyl
acetate:isopropyl alcohol:deionized water (18 meg ohm).
[0289] The wipes are made as follows: mixed and thoroughly stirred
and stored in an amber bottle with a teflon lined cap to minimize
contamination and evaporation.
[0290] Each individual's blood glucose is determined by LSII method
at the time of testing. MM's blood glucose measured as 96 mg/dl,
and JM's blood glucose is 100 mg/dl. In detailing the reflectance
from the glucose patches, a reflectometer having the specification
described herein is used.
[0291] In carrying out the procedure, each individual's targeted
skin area, to which the patch is applied, is first thoroughly
cleansed by wiping with deionized water. Following cleansing, in
one test, the five different gels glucose patches are applied
directly to the cleansed skin area without first wiping with a
wipe. In all other tests, the cleansed skin area is first
pretreated with one of the six wipes. In pre-treating the skin
area, a liberal amount of a wipe is applied by a ChemWipe.TM.. If
too much is applied, the excess amount is removed with a dry
ChemWipe.TM..
[0292] The five different gel glucose patches are then applied to
the wiped skin area within ten seconds after wiping. Before
applying the gel to the cleansed skin area, the dry chemical
glucose membrane is brought into continuous contact with the gel to
uniformly wet the dry chemical glucose membrane. The patch is in
contact with the cleansed skin area for about 5 minutes, at which
time the color change of the membrane is read by reflectance by the
meter to detect the glucose in the interstitial fluid of MM and JM.
The reflectance values for MM and JM with respect to each gel and
wipe are recited in the bar graphs depicted in FIGS. 21, 22, 23,
24, and 25 on the following tables, respectively. The numbers for
the gels and wipes designated herein correspond to the numbers in
FIGS. 21, 22, 23, 24 and 25.
TABLE-US-00014 MM GEL WIPE 1 2 3 4 5 6 7 1 2504 2399 2415 2428 2411
2388 2456 2 2542 2463 2465 2428 2463 2433 2494 3 2471 2542 2529
2549 2561 2545 2590 4 2684 2454 2640 2467 2493 2405 2443 5 2480
2449 2516 2431 2468 2452 2385
TABLE-US-00015 JM GEL WIPE 1 2 3 4 5 6 7 1 2495 2519 2398 2463 2468
2481 2478 2 2557 2532 2532 2488 2628 2545 2486 3 2526 2578 2551
2525 2604 2578 2532 4 2507 2520 2635 2556 2528 2478 2613 5 2502
2636 2633 2593 2438 2386 2585
Example 8
[0293] The following skin permeation enhancers are tested for
permeation enhancing power. The skin is first wiped with a pad
wetted with one of the following permeation enhancer formulations.
A glass cylinder is then secured by o-ring seal against the wiped
area of skin and a defined volume of distilled water is added to
the inside of the glass cylinder (see FIG. 26). After five minutes
of water contact with the skin, the water is removed and its
glucose concentration analyzed by High Performance Liquid
Chromatography with a Bioanalytical Systems, Inc. Enzymatic
detector system. The ratio of glucose detected relative to the
amount detected using a distilled water wipe (control) is used to
evaluate the permeation enhancing power of each formulation. HPLC
results are as follows:
TABLE-US-00016 Skin Permeation Enhancer Ratio to Water Results 1)
20% Salicylic Acid in 50:50-- 7.02 .fwdarw. 10.9 Isopropyl
Alcohol:Deionized Water 2) Tween 80 3.5 .fwdarw. 6.5 3) Limonane 1
.fwdarw. 5.7 4) Isopropyl Alcohol 1.1 .fwdarw. 1.8 5) Acetone 1.1
.fwdarw. 1.8 6) 1:1:1-Ethyl Acetone:Isopropyl 1 .fwdarw. 2.3
Alcohol:Water 7) 90:5:5-Isopropyl Alcohol:Tween 1.7 .fwdarw. 8
80:Limonene 8) 10% Lactic Acid in Isopropyl Alcohol 4 .fwdarw. 11
9) 90% Lactic Acid and 10% Tween 80 7 .fwdarw. 16
[0294] In parallel with the chromatographic studies of Example 7, a
certain permeation enhancer formulation is evaluated by auditioning
it as a prewipe in conjunction with actual glucose monitoring
patches. The performance of a certain permeation enhancer
formulation is evaluated by comparing to the results obtained with
a distilled water prewipe. The formulation gave reproducible
results in replicate determinations, as shown in FIG. 27.
Example 9
[0295] Next, patient results obtained with various transdermal
patches are compared to those obtained using a commercial
fingerstick blood glucose monitor. Oral glucose tolerance tests are
performed (i.e., baseline readings are performed on fasting
volunteers who drank 50-75 grams of glucose and who are then
retested periodically over the course of three hours). Both the
baseline and the subsequent measurements are made with the glucose
patch and with a commercial fingerstick blood glucose system. See
FIG. 28. The glucose patch gels in this experiment are 1%
Carbopol.RTM. and 10% propylene glycol in deionized water (18 meg
ohm).
Example 10
[0296] Once the glucose from the interstitial fluid diffuses into
the patch matrix material, it is quantitated enzymatically using
glucose oxidase and peroxidase on preferably, a polyethersulphone
membrane. The colored product of the peroxidase reaction,
o-tolidine, is then measured by optical reflectometry. This
measurement may be performed either kinetically by measuring the
change in optical density at timed intervals, or else may be
determined at a single fixed-time endpoint of five minutes. The
latter method is the one utilized herein. The enzyme cascade and
color development system is well-characterized herein. This
chemistry system gives accurate and reproducible results when
evaluated either by eye or by reflectometry, and the stability is
shown to exceed one year. Reproducible slopes are obtained for
standard curves, indicated that stored calibrations may be used to
convert photometer millivolt readings into glucose concentrations
expressed as mg/dl. The sensitivity of the device appears to be
approximately 0.5 mg/dl, as shown in FIG. 20.
[0297] The glucose concentrations tested and shown in FIG. 29 are
prepared as follows. A stock glucose solution of 1000 mg/dl is
first prepared. A sample of this stock solution is then diluted in
dH.sub.20 (18 meg ohm) to achieve a desired glucose concentration.
Each glucose concentration made is tested and illustrated in FIG.
29. The individual glucose concentrations are then diluted 1:50 in
a 1% carboxy polymethylene and 10% propylene gel of the present
invention for testing. According to FIG. 29, the sensitivity of the
glucose systems of the present invention appears to be at about 0.5
mg/dl or 5 meg/ml as indicated above and shown in FIG. 29.
Example 11
[0298] The results of the comparison of a standard finger prick
method with glucose patch subjects are depicted in FIGS. 30-33. The
gels are a 1% Carbopol.RTM. gel. Prior to application of the
glucose patch, the targeted skin area is wiped with propylene
glycol.
[0299] The subject in FIG. 30 receives a glucose load approximately
10 minutes after the first glucose level test is performed. As
expected, after the glucose load, this subject's glucose level
rises, as indicated in FIG. 30 by both the standard finger prick
method and the glucose patch.
[0300] The subject in FIG. 31 intakes a high sugar meal
approximately 20 minutes after the first glucose level test is
performed. As shown in FIG. 31, there is an elevation in this
subject's glucose level after consumption of the high sugar
meal.
[0301] In FIG. 32, the subject receives a meal at about 50 minutes
after the first glucose level tests. Slight elevation in glucose
level is observed in FIG. 32.
[0302] In FIG. 33, a subject receives a glucose load at about 20
minutes after the first glucose tests. In spite of glucose load,
little elevation in glucose level is observed, probably due to the
hard work in which the subject was engaged during the testing, as
shown by both the glucose patch and the standard finger prick
method in FIG. 33.
[0303] These results demonstrate good correlation between the
glucose patch and the standard prick method over a glucose range of
50-200 mg/dl.
Example 12
[0304] The results of the comparison of two standard finger stick
methods, i.e., Blood LSP and Blood LSII, with glucose patch
subjects are depicted in FIGS. 34-35. In all subjects, except the
subjects depicted in FIGS. 37 and 44-45, no wipe is sued. The
subjects in FIGS. 37 and 44-45 prewiped with a propylene wipe. The
gels loaded into the glucose patches of this Example 12 are a 1%
Carbopol.RTM. and 10% propylene glycol gel in deionized water (18
meg ohm). The results show good correlation between the two
standard finger stick methods, i.e., Blood LSP and Blood LSII, with
the glucose patches over a glucose range of about 75 mg/dl to about
350 mg/dl.
Example 13
[0305] Three distinct gels are tested in six subjects for
permeation and diffusion enhancement. The three gels are 1%
Carbopol.RTM. (CAR), 1% Carbopol.RTM. and 10% propylene glycol in
deionized water (18 meg ohm) (CARPG) and 1% Carbopol.RTM. and 10%
sodium lauryl sulfate in deionized water (18 meg ohm). In testing
the gels, they are loaded into glucose patches and placed in
contact with skin for about 5 minutes for glucose diffusion to the
membrane for chemical reaction and detection. The results are shown
in FIG. 46 while all three gels are effective, FIG. 46 depicts
that, in all but one subject, the 1% Carbopol.RTM. and 10%
propylene glycol gel is more effective.
[0306] The invention described herein extends to all such
modifications and variations as will be apparent to the reader
skilled in the art, and also extends to combinations and
subcombinations of the features of this description and the
accompanying FIGS. Although preferred embodiments of the methods
and apparatus of the present invention have been illustrated in the
accompanying FIGS. and described in the foregoing Detailed
Description, it will be understood that the invention is not
limited to the embodiments disclosed, but is capable of numerous
rearrangements, modifications and substitutions without departing
from the spirit of the invention as set forth and defined by the
following claims.
[0307] Having described our invention, we claim:
* * * * *