U.S. patent application number 12/188918 was filed with the patent office on 2009-03-12 for monitoring method and/or apparatus.
This patent application is currently assigned to The Regents of the University of California. Invention is credited to Dorian Liepmann, Albert Pisano, Boris Stoeber, Stefan Zimmermann.
Application Number | 20090069651 12/188918 |
Document ID | / |
Family ID | 37011303 |
Filed Date | 2009-03-12 |
United States Patent
Application |
20090069651 |
Kind Code |
A1 |
Zimmermann; Stefan ; et
al. |
March 12, 2009 |
MONITORING METHOD AND/OR APPARATUS
Abstract
A method and apparatus for substance monitoring. One application
is an easy to handle continuous glucose monitor using a group of
hollow out-of-plane silicon microneedles to sample substances in
interstitial fluid from the epidermal skin layer. The glucose of
the interstitial fluid permeates a dialysis membrane and reaches a
sensor. Using MEMS technology, for example, allows well-established
batch fabrication at low cost.
Inventors: |
Zimmermann; Stefan;
(Stockelsdorf, DE) ; Stoeber; Boris; (Berkeley,
CA) ; Liepmann; Dorian; (Lafayette, CA) ;
Pisano; Albert; (Danville, CA) |
Correspondence
Address: |
QUINE INTELLECTUAL PROPERTY LAW GROUP, P.C.
P O BOX 458
ALAMEDA
CA
94501
US
|
Assignee: |
The Regents of the University of
California
|
Family ID: |
37011303 |
Appl. No.: |
12/188918 |
Filed: |
August 8, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10828510 |
Apr 19, 2004 |
7415299 |
|
|
12188918 |
|
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60464221 |
Apr 18, 2003 |
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Current U.S.
Class: |
600/316 ;
600/309; 600/365 |
Current CPC
Class: |
A61B 2562/028 20130101;
A61B 5/14525 20130101; A61B 5/14532 20130101; A61B 5/1486 20130101;
A61B 5/14514 20130101; A61B 2560/0223 20130101 |
Class at
Publication: |
600/316 ;
600/365; 600/309 |
International
Class: |
A61B 5/00 20060101
A61B005/00 |
Goverment Interests
[0002] The Invention was made with government support under Grant
(Contract) No. F30602-00-2-0566 awarded by the Department of
Defense. The Government has certain rights to this invention.
Claims
1. A method of monitoring one or more substances of interest
comprising: applying a plurality of out-of-plane microneedles to a
surface of an internal region, said microneedles long enough to
prestress a region of the surface at a needle lumen; applying high
pressure to a small local surface region through said microneedles
to cause rupture of the cell matrix to open a connection between
fluids inside the needle lumen and bodily fluids underneath the
broken skin layer; and using said connection to sample one or more
substances of interest at and/or just below said surface.
2. The method of claim 1 further wherein: said microneedles
comprising one or more membranes on a side opposite a side applied
to said surface such that said membrane is not placed under said
surface; said membrane separating in said microneedles from a
dialysis material; such that dialysis occurs outside of said
internal region.
3. The method of claim 2 further wherein: said one or more dialysis
membranes comprise a large total membrane surface that can remain
outside of said internal region.
4-5. (canceled)
6. The method of claim 1 further wherein: said surface is a surface
of a living organism or part or organ thereof.
7. The method of claim 1 further wherein: a plurality of said
microneedles are pre-filled with a fluid before said applying.
8. The method of claim 1 further comprising: treating glucose
disorders by applying a plurality of out-of-plane microneedles to
the skin with a dialysis membrane remaining outside the skin
thereby allowing for continuous glucose monitoring.
9. The method of claim 8 further comprising: fixing a detecting
substance useful in determining glucose levels on an opposite side
of said dialysis membrane from said needles; wherein said fixing is
accomplished by placing a polymer-detecting substance solution at
an opposite side of said membrane after higher temperature
fabrication and/or assembly steps of said microneedles have been
performed.
10. A device for monitoring a substance of interest comprising: a
group of out-of-plane microneedles; a dialysis membrane proximal to
a non-insertive side of said group; a dialysis fluid in contact
with a second surface of said dialysis membrane opposite said
group; such that when said group is pressed against a surface of
interest, said substance of interest within and/or behind said
surface of interest can come in contact with a second surface of
said dialysis membrane, allowing one or more substances of interest
to pass into said dialysis fluid.
11. The device according to claim 10 further comprising: one or
more sensors in contact with said dialysis fluid for measuring
and/or detecting one or more substances of interest.
12. The device according to claim 11 further comprising: an area
for holding calibration fluid; and a valve between said calibration
fluid and said dialysis fluid.
13. The device according to claim 10 further comprising: at least
50 microneedles in said group. said microneedles are between about
100 micrometers and about 300 micrometers long. said microneedles
are between about 180 micrometers and about 220 micrometers long.
said microneedles are constructed of one or more of a metallic
material; plastic; silicon; a semiconductor material; said membrane
comprises a polymer and/or gel and/or porous poly-Si; wherein one
or more enzymes integrated into said membrane.
14-28. (canceled)
29. A method of in-device patterning of a temperature sensitive
substance in an integrated system comprising: performing one or
more high temperature steps; placing a solution of said temperature
sensitive substance and a polymer in desired regions of said
integrated system; and gelling and/or immobilizing and/or
polymerizing said solution in regions of interest using
electromagnetic energy.
30. The method of claim 29 further comprising: using a mask to
define areas where said solution will not be immobolized and/or
polymerized and/or gelled; and rinsing away remaining solution.
31. The method of claim 29 further wherein: said temperature
sensitive substance comprises an enzyme. said electromagnetic
energy comprises UV light. said polymerizing comprises crosslinking
said polymer.
32-33. (canceled)
34. The method of claim 29 further comprising: performing one or
more high temperature steps including a step of bonding a
transparent or semi-transparent material on said system; placing a
solution of said temperature sensitive substance and a polymer in
desired regions of said integrated system such that said solution
in part resides in areas between said transparent or
semi-transparent material and other components of said system;
hardening said solution in regions of interest using
electromagnetic energy that can pass through said transparent or
semi-transparent material; and rinsing unhardened portions of said
solution.
35. The method of claim 34 further wherein: said bonding is anodic
bonding; said hardening comprises crosslinking said polymer;
36. The method of claim 34 further wherein: said polymer comprises
PVA-SbQ; said electromagnetic energy comprises UV light; said UV
light comprises light of about 365 nm or 900 mJ/cm2;\
37. The method of claim 34 further wherein: using a mask to define
regions of said hardening; such that said temperature sensitive
substance becomes entrapped in locally formed gel regions; and said
rinsing comprises rinsing unlinked solution.
38-39. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional of 10/828,510, filed Apr.
19, 2004, which claims priority from provisional patent application
60/464,221 filed 18 Apr. 2003, both incorporated herein by
reference for all purposes.
COPYRIGHT NOTICE
[0003] Pursuant to 37 C.F.R. 1.71(e), Applicants note that a
portion of this disclosure contains material that is subject to
copyright protection (such as, but not limited to, source code
listings, screen shots, user interfaces, or user instructions, or
any other aspects of this submission for which copyright protection
is or may be available in any jurisdiction.). The copyright owner
has no objection to the facsimile reproduction by anyone of the
patent document or patent disclosure, as it appears in the Patent
and Trademark Office patent file or records, but otherwise reserves
all copyright rights whatsoever.
BACKGROUND OF THE INVENTION
[0004] The discussion of any work, publications, sales, or activity
anywhere in this submission, including in any documents submitted
with this application, shall not be taken as an admission that any
such work constitutes prior art. The discussion of any activity,
work, or publication herein is not an admission that such activity,
work, or publication existed or was known in any particular
jurisdiction.
[0005] Currently proposed systems for monitoring substances of
interest, such as glucose, using small sampling and monitoring
devices have a number of difficulties. For example, a microdialysis
probe discussed for glucose monitoring in U.S. Pat. No. 6,091,976,
July 18, 2000 (M. Pfeiffer and U. Hoss) is a needle-type probe with
dialysis fluid flowing in and out of the probe. The probe is
inserted at a length of several millimeters underneath the skin at
a shallow angle so that the probe stays in the epidermal tissue. A
dialysis membrane separates the probe interior from the
interstitial fluid surrounding the probe. This membrane allows
diffusion of substances such as glucose from the interstitial fluid
into the dialysis fluid flowing in and out of the probe. The
interstitial fluid is not extracted. The dialysis fluid is then
pumped to a sensor placed downstream where the glucose level of the
dialysis fluid is determined. The glucose concentration of the
dialysis fluid has been found to correlate with the glucose level
in the interstitial fluid.
[0006] Despite the name microdialysis probe in this instance, the
probe dimensions are in the millimeter range. In these proposals,
the reason for using such a long probe is that the area of the
dialysis membrane generally defines the amount of glucose diffusing
into the dialysis fluid during a given amount of time. Generally,
the detection limit of practicable glucose sensors requires a
certain amount of glucose in the dialysis fluid to get reliable
sensor signals. The required membrane area necessary for sufficient
glucose diffusion and high sensor signals is several square
millimeters and this membrane generally defines the size of the
probe, which explains the large dimensions of the dialysis probes
and/or needles in these discussions.
[0007] A disadvantage of using a large "micro" dialysis probe is a
generally painful insertion procedure that generally requires
trained personnel to implant the probe underneath the skin. Thus,
present microdialysis proposals do not easily allow for painless
everyday usage.
[0008] According to the World Health Organization the per capita
diabetes rate in the US increased from 5.2% (world: 2.4%) in 1995
to 6.0% (2.9%) in 2000, and it is expected to reach 8.4% (4.5%) in
2030. While diabetes is the leading cause of blindness, kidney
failure and non-traumatic amputation of the lower limp, other
severe complications associated with hyperglycemia (high glucose
levels) and hypoglycemia (low glucose levels) are nerve damage,
heart disease, coma and brain damage. The traditional fingerstick
test typically takes periodic samples, but this monitoring can miss
periods of hyperglycemia and hypoglycemia, especially during sleep.
This health risk can be avoided using a continuous glucose
monitor.
[0009] Currently available continuous glucose monitoring systems
include the Cygnus GlucoWatch.RTM. and the Minimed CGMS.TM..
However, it is believed that these systems cannot provide an
accurate everyday glucose level control and still require periodic
fingerstick tests for sensor recalibration. The GlucoWatch.RTM. is
easy to use but it relies on reverse iontophoretic interstitial
fluid sampling through the skin, which is affected by fluctuating
skin permeability as described in K. R. Pitzer, S. Desai, T. Dunn,
S. Edelman, Y. Jayalakshmi, J. Kennedy, J. A. Tamada, R. O. Potts,
Detection of Hypoglycemia with the GlucoWatch Biographer, Diabetes
Care, Vol. 24, No. 5, 2001
[0010] The CGMS.TM. is generally not designed for daily usage; it
requires trained personnel to insert the sensor under the skin, as
described in E. Cheyne, D. Kerr, Making `sense` of diabetes: using
a continuous glucose sensor in clinical practice, Diabetes Metab
Res Rev, 18 (Suppl. 1), 2002.
[0011] While frequent and long periods of hyperglycemic blood
glucose levels can account for many long-term complications,
hypoglycemia can cause sudden coma and brain damage. Periodic
fingerstick tests often fail to detect all hypoglycemic and
hyperglycemic events since glucose levels can change rapidly. In
particular, nocturnal hypoglycemia often remains undetected.
SUMMARY
[0012] The present invention, in specific embodiments, involves
novels methods for minimally invasive monitoring. In further
embodiments, the invention provides a device and/or method for
detecting and or monitoring substances of interest, particular
substances in biological research and/or clinical settings. In
further embodiments, the invention provides a device and/or method
using dialysis and out-of-plane microneedles to provide an improved
sensor.
[0013] In more specific embodiments, the invention involves a
method and/or apparatus for monitoring of substances in
interstitial fluid under the skin of a human or animal or under the
outer layer of a plant using out-of-plane microneedles. For humans
and animals, this can allow painless everyday usage.
[0014] In specific embodiments, the invention can be distinguished
from proposals describing generally a single microdialysis probe or
needle. In the present invention, it is not necessary to insert a
dialysis probe or needle underneath the skin. In specific
embodiments of the invention, the dialysis portion of the device
remains outside of the body, even in a very small monitoring
system.
[0015] In other embodiments the invention relates generally to a
method and apparatus for continuous monitoring of compounds in the
epidermal interstitial fluid. As a specific example, the invention
relates to a minimally invasive method for sampling compounds from
the epidermal interstitial fluid using hollow out-of-plane
microneedles and the apparatus for sampling and analyzing these
compounds. A particular application of this invention is to
continuously monitor the epidermal interstitial fluid glucose
level.
[0016] In further specific embodiments, the invention involves an
array (used herein to indicate any type of grouping) of
out-of-plane microneedles that vertically penetrate a skin or other
surface. In specific applications, the microneedles are
approximately 200 .mu.m long, which, for example, is sufficient to
reach the epidermal interstitial fluid in humans. In further
embodiments, the invention involves microneedles that are
pre-filled with a liquid, such as a buffer solution, resulting in a
liquid-liquid interface between the liquid inside the needle and
the interstitial fluid once the needle is inserted. Substances from
the interstitial fluid such as glucose can diffuse into the lumens
of the out-of-plane microneedles. In further embodiments, a
dialysis membrane is placed on an opposite side of a substrate from
the microneedles. Thus, the membrane separates the needle lumens
from the dialysis fluid, which is pumped past the membrane to the
glucose sensor. The amount of glucose diffusing through the
out-of-plane microneedles, through the membrane and into the
dialysis fluid is generally defined by the total area where
diffusion can take place. This area is defined by the total cross
section of all needle lumens.
[0017] In further example embodiments, a group of microneedles in
included in a system along with a system and/or method for
automatic calibration. Automatic calibration allows the system to
provide reliable monitoring results without the need for additional
calibration methods, such as a needle-stick test. According to
specific embodiments of the invention, the dialysis system use in
combination with the out-of-plane microneedles facilitates sensor
recalibration.
[0018] The present invention in specific embodiments provides a
disposable sensor system that is minimally invasive and provides
accurate sensor readings and painless and easy sensor application.
An example of such a system system consists of hollow out-of-plane
microneedles to sample glucose from the interstitial fluid of the
epidermis, an integrated dialysis membrane and an integrated
electrochemical enzyme-based flow-through glucose sensor.
[0019] In a further and very specific example embodiment, an array
of between about 600 to 1500 microneedles is placed on an
approximately 8 mm.times.8 mm substrate. One advantage of using an
array of out-of-plane microneedles is that the resulting membrane
area is large enough for effective diffusion but the insertion of a
number of out-of-plane microneedles is painless since the needles
are in fact very small, actually in the micro-meter range. In
addition the needle array is easy to apply by fixing (e.g., by
taping) or pressing the device onto the skin rather the inserting a
dialysis probe at a shallow angle several millimeter long
underneath the skin. According to specific embodiments of the
invention, a monitoring device using microneedles can be applied to
the skin and effectively sample substances in interstitial without
penetrating deeply enough to impact nerve endings.
[0020] While example detectors according to specific embodiments of
the present invention are described herein as used for performing a
biological assay, it will be understood to those of skill in the
art that a detector according to specific embodiments of the
present invention can be used in a variety of applications for
detecting substances of interests. These applications include, but
are not limited to: detecting contaminants in foodstuffs; detecting
ripeness and/or the presence of sugars in plants or plant parts;
detecting the presence of a desired substance (such as petroleum
components) in an exploration operation; insuring the presence of
desired elements in a manufacturing product, etc.
[0021] The invention and various specific aspects and embodiments
will be better understood with reference to drawings and detailed
descriptions provided in this submission. For purposes of clarity,
this discussion refers to devices, methods, and concepts in terms
of specific examples. However, the invention and aspects thereof
may have applications to a variety of types of devices and systems.
It is therefore intended that the invention not be limited except
as provided in the attached claims and equivalents.
[0022] Furthermore, it is well known in the art that systems and
methods such as described herein can include a variety of different
components and different functions in a modular fashion. Different
embodiments of the invention can include different mixtures of
elements and functions and may group various functions as parts of
various elements. For purposes of clarity, the invention is
described in terms of systems that include different innovative
components and innovative combinations of innovative components and
known components. No inference should be taken to limit the
invention to combinations containing all of the innovative
components listed in any illustrative embodiment in this
specification.
[0023] In some of the drawings and detailed descriptions below, the
present invention is described including various parameters of
dimension and/or other parameters. These should be understood as
illustrating specific and possible preferred embodiments, but are
not intended to limit the invention. Many devices and/or methods
have variations in one or more of the detailed parameters described
herein will be apparent to persons of skill in the art having the
benefit of the teachings provided herein and these variations are
included as part of the present invention.
[0024] All references, publications, patents, and patent
applications cited and/or provided with this submission are hereby
incorporated by reference in their entirety for all purposes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a schematic diagram of an example
microneedle-based continuous monitor wherein microneedle lumens are
filled with interstitial fluid by capillary action and a substance
of interest diffuses through the integrated dialysis membrane into
dialysis fluid that is pumped past an integrated enzyme-based
flow-through sensor according to specific embodiments of the
invention.
[0026] FIG. 2 is a schematic diagram of an example simplified
microneedle-based monitor wherein a pre-filled system allows
glucose diffusion through the microneedles to an integrated
two-electrode enzyme-based sensor according to specific embodiments
of the invention.
[0027] FIG. 3 is a schematic diagram of an example
microneedle-based continuous monitor including a separate
calibration fluid system according to specific embodiments of the
invention.
[0028] FIG. 4 illustrates an example schematic diagram of a sensor
system showing three representative microneedles, a dialysis
membrane, fluid reservoirs and pumps, according to specific
embodiments of the present invention.
[0029] FIG. 5 illustrates an example microneedle component with a
crosslinked polymer used as a dialysis membrane and an active
membrane optionally with immobilized enzymes according to specific
embodiments of the invention.
[0030] FIG. 6 illustrates an example sensor response to a fast
decreasing glucose level (2.25 mg/dl/min) showing that the time lag
of the sensor response is approximately 2 min and thus, a
hypoglycemia alarm could be triggered at 54.7 mg/dl according to
specific embodiments of the invention.
[0031] FIG. 7 illustrates the electrical operation of an example
enzyme-based electrochemical glucose sensor that can be used in
systems and/or devices according to specific embodiments of the
invention.
[0032] FIG. 8 illustrates an example of data showing sensor
calibration (left) according to specific embodiments of the present
invention.
[0033] FIG. 9 illustrates an example device with approximately 1000
microneedles and other components according to specific embodiments
of the present invention.
[0034] FIG. 10 is a scanning electron micrograph showing an example
microneedle configuration of one configuration according to
specific embodiments of the invention.
[0035] FIG. 11 is a scanning electron micrograph showing an example
of an alternative microneedles configuration (e.g., needles are
approximately 270 .mu.m long, 100 .mu.m wide shaft, ID=50 .mu.m,
400 .mu.m pitch) that can be used in a dialysis system according to
specific embodiments of the invention.
[0036] FIG. 12 is a schematic diagram of a skin penetration method
using hollow out-of-plane microneedles according to specific
embodiments of the invention.
[0037] FIG. 13 is a schematic diagram of a skin penetration method
using a pre-bent elastic plate with through holes according to
specific embodiments of the invention.
[0038] FIG. 14 illustrates aspects of a novel technique for
in-device enzyme immobilization which in this particular example is
based on poly(vinyl alcohol)-styrylpyridinium, a water-soluble
photosensitive polymer containing enzymes according to specific
embodiments of the present invention. The figure can be understood
to illustrate an sensor/dialysis portion of a sensor system to
which a microneedle array may be attached.
[0039] FIG. 15A-B illustrates an example wafer stack with auxiliary
channels for filling according to specific embodiments of the
present invention.
[0040] FIG. 16 illustrates an immobilized heat-sensitive substance
in side pockets of a flow channel according to specific embodiments
of the present invention.
[0041] FIG. 17 illustrates an immobilized heat-sensitive substance
around pins inside a is flow channel according to specific
embodiments of the present invention.
[0042] FIG. 18 is a block diagram showing a representative example
logic device in which various aspects of the present invention may
be embodied.
[0043] FIG. 19 (Table 1) illustrates an example of diseases,
conditions, or statuses for which substances of interest can
evaluated according to specific embodiments of the present
invention.
DESCRIPTION OF SPECIFIC EMBODIMENTS
1. Definitions
[0044] The following definitions may be used to assist in
understanding this submission. These terms, as well as terms as
understood in the art should be used as a guide in understanding
descriptions provided herein.
[0045] A "substrate" is a, preferably solid, material suitable for
the attachment of one or more molecules. Substrates can be formed
of materials including, but not limited to glass, plastic, silicon,
germanium, minerals (e.g. quartz), semiconducting materials (e.g.
silicon, germanium, etc.), ceramics, metals, etc.
2. Overview of the invention
[0046] According to specific embodiments, the present invention
involves methods, devices, and systems that enable a new approach
to monitoring substances of interest from within an environment
(such as a plant or animal) by using out-of-plane microneedles and
a sensing method that is substantially external to the environment
in which a substance is being monitored. A primary application is
continuous glucose monitoring in humans, though other applications
are contemplated.
[0047] Integrated systems and/or methods of the invention generally
comprise an array of out-of-plane microneedles that are inserted
into an area to be sensed (such as skin), and integrated into the
non-inserted side of the microneedles one or more sensing
components. The microneedles can be of various configurations,
examples of which are described herein. The sensing components in
their most simple state can include a prefilled buffer reservoir
with chemical and/or electrical sensor components. Other systems
can include dialysis elements, electronic controls, small scale or
microfluidic channels, pumps, and systems, dialysis components
and/or calibration components. A number of example configurations
of such integrated systems are described in detail below.
[0048] The invention is also involved with a number of novel
techniques and/or devices that enable or improve such monitoring
systems in particular embodiments. These techniques and/or devices
have applications and uses in different systems than the examples
given here, as will be understood by those of skill in the art from
these teachings and in some cases are independently novel.
3. Example System Configurations
[0049] To provide different contexts for understanding embodiments
of the present invention, various example embodiment of sensing
systems or portions thereof according to specific embodiments of
the invention are illustrated in FIG. 1 through FIG. 5
[0050] In each case, these figures schematically represent the
combination of out-of-plane microneedle arrays with other
components to form a microneedle array detection system. Note that,
in each of these illustrations, the one to three microneedles
illustrated should be understood to represent an array of generally
tens, hundreds, or a thousand or more microneedles as illustrated
below. In some embodiments, a large set, up to all available
microneedles, may be integrated with a single detection system at
the base of the needle. In other systems, two or more separate
detection systems can be integrated at the base of a single
microneedle array, either to provide different sensing, for ease of
use or manufacturing, for staged use, or to provide a control
system.
[0051] Dialysis
[0052] FIG. 1, FIG. 3, FIG. 4, and FIG. 5 each illustrate different
embodiments of a sensor system that includes a dialysis membrane to
separate the sensing area from the sample area. This is a presently
preferred embodiment. Dialysis is a well known technique for using
a selectively permeable membrane between two fluids to allow
diffusion of a desired substance while preventing diffusion of
other substances. One example membrane that can be used in systems
according to specific embodiments of the invention is an integrated
porous polysilicon dialysis membrane, as will be understood in the
art. Other example membrane technology will be understood from the
description herein and cited references. In systems according to
specific embodiments of the invention, the dialysis membrane is any
membrane or system or structure that allows diffusion of a
substance that is intended to be detected and prevents one or more
possibly interfering substances.
[0053] Diffusion
[0054] FIG. 2 is a schematic diagram of an example simplified
microneedle-based monitor wherein a pre-filled system allows
glucose diffusion through the microneedles to an integrated
two-electrode enzyme-based sensor according to specific embodiments
of the invention. While this system may not have the lifetime or
reliability of the dialysis-based systems in human applications, it
has proven valuable as a prototyping design and has applications
where ease of manufacturing and/or reduced cost are primary
considerations or where the sensor is used in applications that do
not involve the presence of proteins or other compounds that can
contaminate the sensing components.
4. Operation Examples
[0055] As an example of operation, in these detectors, glucose or
another substance of interest that is present in blood or
interstitial fluid diffuses into the microneedles. This transport
may be facilitated by prefilling the microneedles with a substance
to aid diffusion (e.g., a buffer fluid or gel) to prevent air
trapped in the needle lumen from blocking fluidic flow or
diffusion. With the lumen in contact with the interstitial fluid,
substances of interest can come in contact with one or more
sensors, such as chemical, electrical, electrochemical, optical,
temperature, etc. sensors. In the example systems, example sensors
include the WE, CE and/or RE electrodes shown in FIG. 1, the
integrated sensor components shown in FIG. 2. Catalysts or reagents
can also be included depending on the type of sensing assay being
used (e.g., the GOX regions shown in the figures).
[0056] Operation Example Details
[0057] A sensor system according to specific embodiments of the
invention can have a number of components depending on the
particular type of sensor used. Systems including dialysis include
a dialysis barrier and can include a dialysis fluid reservoir,
fluidic channels, micropumps and values as shown. Systems including
a calibration system can include a calibration fluid reservoir,
fluidic channels, micropumps and values as shown. In some
embodiments, calibration fluid is segregated from sample or
dialysis fluid by a moveable valve or by a flow restriction valve
as shown. In alternative embodiments, calibration can be
accomplished by changing the flow rate of dialysis fluid and using
that fluid for calibration.
Example 1
[0058] FIG. 1 is a schematic diagram of an example
microneedle-based continuous monitor wherein microneedle lumens are
filled with interstitial fluid by capillary action and a substance
of interest diffuses through the integrated dialysis membrane into
dialysis fluid that is pumped past an integrated enzyme-based
flow-through sensor according to specific embodiments of the
invention. In this example, an array of hollow out-of-plane
microneedles is used to penetrate the skin and to interface with
the interstitial fluid. A dialysis membrane separates the
interstitial fluid and the dialysis fluid; thus, no interstitial
fluid is extracted during operation. Dialysis fluid with a known
constant glucose concentration is continuously pumped past the
dialysis membrane and an integrated sensor (e.g., for glucose).
Glucose diffuses through the microneedles and through the dialysis
membrane into or out of the dialysis fluid. The concentration
change in dialysis fluid is measured--it depends on the flow rate
of the dialysis fluid and the glucose concentration in the
interstitial fluid. At high flow rates (recalibrating mode) the
amount of glucose diffusing into the dialysis fluid is negligible
so that the glucose concentration of the dialysis fluid remains
unchanged. Thus, a known concentration is measured and the sensor
can be recalibrated. At low flow rates (measuring mode) the
concentration in the dialysis fluid changes significantly--the
change in glucose concentration corresponds to the glucose
concentration in the interstitial fluid.
Example 2
[0059] FIG. 3 is a schematic diagram of an example
microneedle-based continuous monitor including a separate
calibration fluid system according to specific embodiments of the
invention. In this further specific example, operation of the
example sensor can be understood as follows. An group of, for
example, about 200 .mu.m long hollow out-of-plane microneedles are
used to penetrate the topmost layer of the skin, allowing their
opening to come in contact with interstitial fluid from the
epidermis. Once the microneedles are either filled with
interstitial fluid or once sufficient time has elapsed for a
substance of interest to diffuse into prefilled needles, the
substance of interest (e.g., glucose) diffuses through the dialysis
membrane into dialysis fluid, keeping unwanted substances (e.g.,
larger protein molecules) outside of the dialysis area, thus
improving the sensor long-term stability.
[0060] Various detection strategies can be used for detecting
substances of interest. Different strategies may be employed in
different embodiments of the invention. As one example, consider
the enzyme-based flow-through glucose sensor shown in FIG. 3. This
sensor includes a Pt working electrode (WE), an Ag/AgCl reference
electrode (RE) and a Pt counter electrode (CE). The glucose oxidase
(GOX) is immobilized upstream from the working electrode inside the
flow channel.
[0061] In this example system, an integrated diffusion barrier
channel prevents glucose diffusion from the calibration fluid into
the dialysis fluid during sensor recalibration. Other types of
barriers, such as moveable valves, etc., can be used in other
embodiments, but a barrier as shown is easy to fabricate and
effective in many situations. The diffusion barrier consisting of a
long and narrow diffusion path prevents diffusion of glucose from
the calibration fluid into the dialysis fluid during sensor
recalibration. In the figure, this barrier is shown with the
diffusion path oriented vertically in the dialysis fluid channel.
While this provides an easy to view illustration, using typical
microfabrication techniques, the diffusion barrier will usually
more easily be fabricated with the diffusion path oriented
horizontally on the substrate and thus the diffusion barrier path
shown in FIG. 3 can be understood as a top down view of that
portion of the system.
[0062] Electrical-Chemical Sensor
[0063] As an example of one type of sensor that can be used in a
microneedle system according to specific embodiments of the
invention, the sensor components shown in FIG. 3 are further
described. In the presence of dissolved oxygen, glucose oxidase
immobilized inside the channel catalyses the oxidation of glucose
to gluconic acid. Hydrogen peroxide is formed as a by-product.
Glucose+O.sub.2Gluconic acid+H.sub.2O.sub.2
[0064] The hydrogen peroxide is detected downstream using an
integrated electrochemical sensor. The working electrode is biased
0.7 V versus the reference electrode. Thus, hydrogen peroxide is
oxidized at the working electrode and the resulting electric
current is proportional to the glucose concentration inside the
dialysis fluid.
H.sub.2O.sub.2O.sub.2+2H.sup.++2e.sup.-
[0065] In this example system, an integrated diffusion barrier
channel prevents glucose diffusion from the calibration fluid into
the dialysis fluid during sensor recalibration. Other types of
barriers, such as moveable valves, etc., can be used in other
embodiments, but a barrier as shown is easy to fabricate and
effective in many situations. The diffusion barrier consisting of a
long and narrow diffusion path prevents diffusion of glucose from
the calibration fluid into the dialysis fluid during sensor
recalibration. In the figure, this barrier is shown with the
diffusion path oriented vertically in the dialysis fluid channel.
While this provides an easy to view illustration, using typical
microfabrication techniques, the diffusion barrier will usually
more easily be fabricated with the diffusion path oriented
horizontally on the substrate and thus the diffusion barrier path
shown in FIG. 3 can be understood as a top down view of that
portion of the system.
[0066] Since the chlorine ion concentration in biological fluids
remains constant at 0.15 mM a simple planar Ag/AgCl electrode can
serve as a pseudo reference electrode. For automatic sensor
recalibration, reference glucose solution is periodically pumped
past the sensor. Thus, no fingerstick tests are required to account
for the usual gradual loss of enzyme activity during the sensor
operation time.
Example 3
[0067] FIG. 4 illustrates an example schematic diagram of a sensor
system showing three representative microneedles, a dialysis
membrane, fluid reservoirs and pumps, according to specific
embodiments of the present invention. In this example system,
separate calibration and dialysis fluids reservoirs are used, with
two micropumps and valves as shown.
Example 4
Microneedle with Cross-Linked Polymer
[0068] FIG. 5 illustrates an example microneedle component with a
crosslinked polymer used as a dialysis membrane and an active
membrane optionally with immobilized enzymes according to specific
embodiments of the invention. In a particular example construction,
the polymer is crosslinked in the flow channel right underneath the
needles where it forms walls around the needle lumen opening from
the bottom to the top of this channel. In this configuration, the
compounds from the interstitial fluid diffuse through the needle
lumen and through the gel wall where they might undergo enzymatic
reactions before getting into the dialysis fluid in the case where
enzymes have been immobilized in this membrane.
[0069] Thus, in this specific example, locally crosslinked polymer
forms walls in the flow channel underneath the needles, separating
the interstitial fluid from the dialysis fluid. Analytes can
diffuse through this polymer.
[0070] Electrical Components
[0071] A prototype system using the glucose as describe above was
tested. FIG. 6 illustrates an example sensor response to a fast
decreasing glucose level (2.25 mg/dl/min) showing that the time lag
of the sensor response is approximately 2 min and thus, a
hypoglycemia alarm could be triggered at 54.7 mg/dl according to
specific embodiments of the invention.
[0072] FIG. 7 illustrates the electrical operation of an example
enzyme-based electrochemical glucose sensor that can be used in
systems and/or devices according to specific embodiments of the
invention. Another example glucose sensor is an integrated glucose
sensor as discussed in M. Lambrechts and W. Sansen, Biosensors:
Microelectrochemical devices, IOP Publishing, New York, 1992. Other
sensor technology can be employed according to specific embodiments
of the invention.
[0073] FIG. 8 illustrates an example of data showing sensor
calibration (left) according to specific embodiments of the present
invention.
[0074] In specific example systems, power supply and signal
processing are achieved with a portable pager size device that
connects to the microsystem. The portable pager sized external
device can also include components for connecting to a computer
and/or information processing system, either through a physical
adaptor or wireless connection. A wireless connected device can be
used in home and or office settings to allow an individual to be
remotely monitored by, for example, a health care provider or elder
care provider. A large number of such monitoring devices can be
used in institutional settings, such as care facilities and/or work
environments and/or hospitals to monitor a number of
individuals.
[0075] Micropumps
[0076] Techniques and/or devices for constructing micropumps are
well-known in the art and in general any micropumping technique can
be included in systems according to specific embodiments of the
invention. Example micropumps that can be used according to
specific embodiments of the invention are discussed in N.-T.
Nguyen, X. Huang, T. K. Chuan, MEMS-Micropumps: A Review, Journal
of fluids Engineering, Vol. 124, 2002.
[0077] Valve
[0078] According to specific embodiments of the invention, a
two-way valve consisting of a diffusion barrier and a check valve
allow pumping either dialysis fluid or calibration fluid to the
sensor is employed. This valve represents a novel design. Other
valve designs can be incorporated in specific embodiments of the
invention. It should be understood that a the diffusion barrier as
illustrated in FIG. 3 is schematically shown perpendicular to a
substrate in order to illustrate its construction. In specific
embodiments, this barrier will be constructed in a plane parallel
to the largest substrate plane.
[0079] Integrated Systems
[0080] An example embodiment was fabricated using fabrication steps
that will be familiar in the art in addition to the teachings
provided herein and in cited references. FIG. 9 illustrates an
example device with approximately 1000 microneedles and other
components according to specific embodiments of the present
invention. Other processes, including processing having printing,
molecular growth and/or other fabrication steps as understood in
the art can also be used to fabricate a device embodying the
invention. Thus, FIG. 9 can also be understood as illustrating an
early prototype of a simplified monitor, which only consists of
out-of-plane microneedles and a glucose sensor.
5. Microneedle Designs
[0081] A number of different methods are known for forming
microneedles and a variety of these methods and different types of
microneedle arrays can be used in a device according to specific
embodiments of the invention. One such device is described in B.
Stoeber, D. Liepmann, Method of Forming Vertical, Hollow Needles
within a Semiconductor Substrate, and Needles Formed thereby, U.S.
Pat. No. 6,406,638, Jun. 18, 2002. Microneedle arrays built using
plastic and metal technology can also be used in a device according
to specific embodiments of the invention.
[0082] FIG. 10 is a scanning electron micrograph showing an example
microneedle configuration of one configuration according to
specific embodiments of the invention. These microneedles can be
used in specific embodiments of the invention and can fabricated as
discussed in U.S. Pat. No. 6,406,638.
[0083] It has been found is some situations, however, that longer
and/or sharper microneedles may provide more easy penetration of
various surfaces. FIG. 11 is a scanning electron micrograph showing
an example of an alternative microneedles configuration (e.g.,
needles are approximately 270 .mu.m long, 100 .mu.m wide shaft,
ID=50 .mu.m, 400 .mu.m pitch) that can be used in a dialysis system
according to specific embodiments of the invention. These needles
can be fabricated using the etching techniques disclosed in U.S.
Pat. No. 6,406,638, but with etching steps modified to achieve
longer and/or sharper needles. This new microneedle design allows
easier penetration of the skin due to a longer needle shaft, which
causes the skin to stretch more and to break the stratum corneum.
In some cases, these longer microneedles may reach the capillary
bed of the dermis so that blood is sampled through the needles
along with or instead of interstitial fluid.
[0084] While etched microneedle designs have been the most studied
so far, other methods for forming microneedles can also be employed
according to specific embodiments of the invention.
[0085] In one such method, a liquid such as a polymeric fluid can
be poured onto a surface with thin pillars perpendicular to this
surface. Different mechanisms can then be used to make this liquid
higher around the pins than further away from them to generate the
needle shape and the pins can then be removed after or during
hardening of the liquid. The liquid could either be poured onto the
molding surface from the top, it could enter from the side, or it
could be pushed onto this surface through bottom holes in this
surface. It is also possible to condensate or to sublime this
material on the molding surface. Capillary action can cause the
liquid to rise up on the surface of the thin pillars, with the
height of rise will depend on the contact angle between the fluid
and the pillars, the surface tension of the fluid and its specific
weight. The liquid can then be hardened in its current
conformation.
6. Breaking Outer Surface or Membrane
[0086] In further embodiments, the invention involves a novel
method for breaking the outer layer of mammalian skin (stratum
corneum) in order to create an interface with bodily fluids. This
method consists of applying a localized high pressure-load to one
or multiple small location on the skin in order to yield the outer
skin layer. This effect can be promoted by applying a preload to
the skin in form of lateral stretching.
[0087] Large hypodermic needles are classic means for the
penetration of mammalian skin. This method has been used for
injection as well as extraction of fluids from organisms. It
requires sharp individual needles, usually made from steel, which
cut through the outer skin layer and open a passage for insertion
of the needle shaft into the tissue. Some proposed microneedle
methods replicate this method on a smaller scale, where needle
shaft lengths were typically less that 1 mm. The target depth in
the tissue is typically not as deep as in the case of hypodermic
needles. It typically ranges from tens to only hundreds of
microns.
[0088] Effort has been spent on generating extremely sharp
microneedles, which cut the skin open in order to allow injection
of fluids into the organism or sampling of bodily fluids in the
same fashion as in the case of hypodermic needles. However,
fabrication of extremely sharp small needles can be difficult and
expensive. Furthermore, it is unclear if the sharp tips of these
microneedles have a sufficient mechanical strength to prevent
breakage during usage. In addition, the skin and the underlying
tissue are very flexible for small deflection as typically caused
by short microneedles, so that the classical approach of cutting
through the stratum corneum risks to fail due to insufficient
contact pressure. This problem is even more severe in the case of
needle arrays, where a distributed load over a wide area of skin
can results in a bed of nails effect, which merely leads to
uniformly pushing down the skin. Nevertheless, microneedles allow
easy integration into advanced drug delivery systems or into
systems for detection of body fluids and/or compounds in an
organism, which could be very important for the future of medical
care.
[0089] A number or alternative methods for skin penetration have
been developed, which use high-speed impact of some material onto
the skin. The skin cannot deform rapidly because of its inertia and
ruptures. A. B. Baker and J. E. Sanders (Fluid mechanics analysis
of a spring-loaded jet injector, IEEE Transactions on Biomedical
Engineering, 46 (2), February 1999, pp. 235-242) used the inertial
force of a thin liquid jet to cut through the skin, M. A. F.
Kendall, P. J. Wrighton Smith and B. J. Bellhouse (Transdermal
ballistic delivery of micro-particles: Investigation into skin
penetration, Proceedings of the 22.sup.nd Annual EMBS International
Conference, July 23-28, Chicago, Ill., USA, pp. 1621-1624, 2000)
and X. L. Yu, X. W. Zhang, Y. Wang, J. Xie and P. F. Hao (Particle
acceleration for delivery deoxyribonucleic acid vaccine into skin
in vivo, Review of Scientific Instruments, 72 (8), pp. 3390-3395,
2001) drove small ballistic particles through the outer skin layer
into deeper tissue, and S. Lee, D. J. McAuliffe, T. Kodama and A.
G. Doukas (In vivo transdermal delivery using a shock tube, Shock
Waves, 10, pp. 307-311, 2000) generated shock waves in order to
enhance drug diffusion into the skin. A more destructive method for
opening the skin uses localized heat to burn a hole into the
stratum corneum (M. Paranjape, J. Garra, S. Brida, T. Schneider, R.
White, J. Currie, "Dermal thermo-poration with a PDMS-based patch
for transdermal biomolecular detection", Technical Digest of the
Solid-State Sensor, Actuator, and Microsystems Workshop 2002,
Hilton Head Island, S. C., USA, June 2-6, pp. 73-76, 2002).
[0090] These results lead to the conclusion that breaking the
stratum corneum with shorter microneedles in order to provide
diagnostic sensing may be improved by using a different mechanism
than simply penetrating the stratum corneum with needles. The
needle tips are rather used to generate high local stress in the
stratum corneum without breaking it, while providing an additional
load on the skin from a pressurized liquid inside the needles to
rupture the skin.
[0091] This mechanism can be used for glucose sampling through the
short microneedles. In this approach, the outer skin layer can be
broken by applying high pressure to a small local skin region,
which results in rupture of the cell matrix. This effect can be
promoted by applying a preload to the skin in form of lateral
stretching. Pressing such a microneedle against the skin as shown
in FIG. 12 (top) stretches the skin over the needle tip, so that
additional pressure applied to the fluid inside the needle lumen
results in yielding of the skin, which ruptures and opens a passage
way between fluids inside the needle lumen and bodily fluids
underneath the broken skin layer, FIG. 12 (middle). The stratum
corneum slips back while the needle tip is inserted into the
epidermis.
[0092] This opened passage can be used for multiple purposes.
Compounds or fluids from within the organism can get transported
through the needle lumen by diffusion or other transport mechanisms
as shown in FIG. 12 (bottom left), so that these compounds can be
detected or quantified for monitoring purposes. Such compounds or
fluids could be glucose, lactate, proteins, lipids, DNA, cells or
blood.
[0093] This flow passage can also be used for injection of fluids
into the organism as shown in FIG. 12 (bottom right). In addition,
this interface with bodily fluids can be used to send and/or
collect electrical or optical signals into or from the organism for
detection purposes. Multiple needles in form of an array can be
used simultaneously for an identical purpose or multiple
applications.
[0094] As a major advantage, this perforation method does not
require extremely sharp microneedles, which allows simpler
fabrication at low cost. Furthermore, less sharp microneedles are
less susceptible to breakage of their tip increasing their
reliability. In addition, the usage of less sharp needles is safer
since they only penetrate skin in response to the combined forces
of stretching the skin and pressurizing the fluid.
[0095] In certain cases it might be possible to apply this method
of skin perforation without using microneedles. FIG. 13 shows an
apparatus that stretches the skin as it is being pressed against
it. The base of this apparatus extends laterally while its edges
hold on to the skin. This base also provides small trough holes,
which can be used to apply additional pressure to the small regions
of the skin underneath these holes by pressurizing a fluid from the
side of the base opposite to the skin. Small rims around these
openings on the side of the skin provide a good seal between the
apparatus and the skin during pressure application.
7. Immobilization Technique
[0096] According to specific embodiments of the invention,
wafer-level fabrication of an integrated system of the invention is
preferably performed using anodic bonding at relatively high
temperatures, such as above about 100.degree. C. However, enzymes
or substances of interest in integrated systems according to
specific embodiments of the invention and in other BioMEMS and
similar systems can be adversely affected at maximum temperatures
well below this temperature. Glucose oxidase, for example,
denatures at temperatures above 60.degree. C.
[0097] Thus, in specific embodiments, the present invention
involves a novel immobilization technique that allows patterning
inside microchannels after bonding or other high-temperature steps
have been performed. This technique is applicable in various
applications, such as other BioMEMS that require high temperature
steps and the integration of heat-sensitive bioactive
materials.
[0098] FIG. 14 illustrates aspects of a novel technique for
in-device enzyme immobilization which in this particular example is
based on poly(vinyl alcohol)-styrylpyridinium, a water-soluble
photosensitive polymer containing enzymes according to specific
embodiments of the present invention. According to specific
embodiments of the invention, an in-device enzyme immobilization
technique uses a photosensitive water-soluble polymer, such as, for
example, PVA-SbQ for example as discussed in K. Ichimura, A
Convenient Photochemical Method to Immobilize Enzymes, Journal of
Polymer Science: Polymer Chemistry Edition, John Wiley & Sons,
Vol. 22, pp. 2817-2828, (1984). This polymer is generally is mixed
with buffer solution (e.g., PBS, pH 7.4) containing a substance of
interest to be immobilized, such as glucose oxidase.
[0099] Basic example fabrication steps can be understood as
follows: (1) High-temperature wafer bonding (e.g., Pyrex to
silicon) and any other high-temperature steps are performed; (2)
Channels are filled with enzyme-polymer solution, and (3)
crosslinking polymer under UV light or other energy source to form
gels in which, optionally, enzymes are entrapped; (4) rinsing out
unlinked solution.
[0100] More specifically, after high temperature processing and/or
fabrication steps (such as, anodic wafer bonding of a Pyrex cover
and silicon base) areas and/or devices can be filled with this
substance-polymer solution. In particular embodiments, auxiliary
channels can be used connecting all regions of interest and thereby
allowing filling of an entire wafer or large area thereof by
capillary force through a single inlet in a short time and
generally without bubble formation. FIG. 15A-B illustrates an
example wafer stack with auxiliary channels for filling according
to specific embodiments of the present invention.
[0101] In further embodiments, the polymer is selectively exposed
to UV light (e.g., at 365 nm (600 mJ/cm.sup.2)) optionally through
a transparent or partially transparent material (e.g., a Pyrex
cover) generally using a shadow mask to cover those areas where it
is not desired to fix the substance. Thus, the substance of
interest (e.g., an enzyme) is entrapped in locally formed gel
regions. In a specific example embodiments, the low absorption of
Pyrex at 365 nm makes an exposure through the glass cover possible.
However a variety of different materials can be used with different
wavelengths of light depending on the wavelength having the desired
effect on the chosen polymer solution. Many combinations of
transparency and useable polymer materials and light wavelengths
can be used in different embodiments of the invention and the
selection of a workable combination of these will be within the
ordinary skill of those in the art having benefit of this
disclosure.
[0102] When desired during fabrication (e.g., after wafer dicing),
the unlinked enzyme-polymer solution can be rinsed out of the chips
by soaking them in buffer solution for several hours.
[0103] Experiments using specific example embodiments show that the
enzyme activity remains constant, which means that only a
negligible amount of enzyme is washed out of the gel while soaking.
Furthermore an example tested gel does not swell and thus will not
block the flow channel during sensor operation when dialysis fluid
flows through the sensor. In particular embodiments, maintenance of
the gel in place is aided by crosslinking it in side pockets or
around pins inside the channel, an example of which is shown in
FIG. 16 and FIG. 17. This assists the gel to be held in place
during operation. Other techniques to enhance gel-adhesion can be
used, such as modifying the surface to which the gel should adhere,
either mechanically (e.g., by introducing roughness in the surface,
etc.) or chemically by changing the chemical properties of the gel
or change the properties of the material and/or surface to which
the gel should adhere.
[0104] In further embodiments, dicing the wafer stack into chips
opens the in-plane fluid ports of each sensor device. Capillary
tubes (=360 .mu.m) can be glued into the fluid ports. Furthermore,
Side pockets or pins (anchors) inside the flow channels can be used
to hold the gel in place when dialysis fluid (buffer) flows through
the channels during sensor operation.
[0105] In a specific example embodiment related to glucose
detection as elsewhere described herein, in order to show that
glucose oxidase is suitable for photochemical immobilization the
effect of UV light (365 nm) on the enzyme activity has been
investigated. No significant decrease in activity could be measured
for exposure energies up to 18000 mJ/cm.sup.2. Thus glucose oxidase
is very insensitive to UV light and the exposure energy of 600
mJ/cm.sup.2 use to crosslink PVA-SbQ has no effect on the enzyme
activity. In addition the enzyme can preserve its activity since it
is only entrapped inside the gel and not crosslinked to it.
[0106] However, in specific embodiments, the effective activity of
the immobilized enzyme is reduced compared to enzyme in solution
due to the diffusion limited glucose concentration inside the gel.
For example, it has been found that the effective activity of
enzyme immobilized in a 1.5 mm thick gel layer with a free surface
of 40 mm.sup.2 and 0.006 U glucose oxidase drops by 70% compared to
0.006 U of free enzyme in buffer solution for the same pH value and
the same glucose concentration of 90 mM. Such activity loss can be
compensated by a suitable sensor design, which guarantees a thin
gel film with a large free surface area. Furthermore a high enzyme
concentration is required in the gel to ensure a diffusion
controlled amperometric current independent of the enzyme activity.
However, a large amount of enzyme results in an oxygen-limited
current at higher glucose concentrations. For a thin film of 5
.mu.l gel containing 0.025 U glucose oxidase the current approaches
saturation at a glucose concentration of about 180 mg/dl
[0107] In further embodiments, the invention can be embodied in
advanced enzyme-based BioMEMS, such as a continuous
self-calibrating glucose monitor. In specific embodiments, the
enzyme is immobilized as discussed above in a micro-scale flow
channel. As will be understood from the above, wafer-level
fabrication of such BioMEMS with integrated fluidic components can
require bonding techniques at elevated temperatures such as anodic
bonding. This conflicts with the high sensitivity of enzymes to
temperature. Glucose oxidase, for instance, starts to denature at a
temperature of about 60.degree. C. Thus, enzyme immobilization
needs to be performed after wafer bonding.
8. Diagnostic Uses
[0108] As described above, following identification and validation
of a sensor for a particular substance, including biological
molecules such as sugars, proteins, fats, or any substance of
interest according to the invention, in specific embodiments such
detectors are used in clinical or research settings, such as to
predictively categorize subjects into disease-relevant classes, to
monitor subjects on a continuous basis to detect a substance of
interest, etc. Detectors according to the methods the invention can
be utilized for a variety of purposes by researchers, physicians,
healthcare workers, hospitals, laboratories, patients, companies
and other institutions. For example, the detectors can be applied
to: diagnose disease; assess severity of disease; predict future
occurrence of disease; predict future complications of disease;
determine disease prognosis; evaluate the patient's risk; assess
response to current drug therapy; assess response to current
non-pharmacologic therapy; determine the most appropriate
medication or treatment for the patient; and determine most
appropriate additional diagnostic testing for the patient, among
other clinically and epidemiologically relevant applications.
Essentially any disease, condition, or status for which a substance
or difference can be detected in an interstitial fluid can be
evaluated, e.g., diagnosed, monitored, etc. using the diagnostic
methods of the invention, see, e.g. Table 1.
[0109] In addition to assessing health status at an individual
level, the methods and diagnostic sensors of the present invention
are suitable for evaluating subjects at a "population level," e.g.,
for epidemiological studies, or for population screening for a
condition or disease.
[0110] Web Site Embodiment
[0111] The methods of this invention can be implemented in a
localized or distributed data environment. For example, in one
embodiment featuring a localized computing environment, a sensor
according to specific embodiments of the present invention is
configured in proximity to a detector, which is, in turn, linked to
a computational device equipped with user input and output
features. In a distributed environment, the methods can be
implemented on a single computer, a computer with multiple
processes or, alternatively, on multiple computers. Sensors
according to specific embodiments of the present invention can be
placed onto wireless integrated circuit devices and such wireless
devices can return data to a configured information processing
system for receiving such devices. Such devices could, for example,
be configured to be affixed to a subject's body.
[0112] Kits
[0113] A detector according to specific embodiments of the present
invention is optionally provided to a user as a kit. Typically, a
kit of the invention contains one or more sensors constructed
according to the methods described herein. Most often, the kit
contains a diagnostic sensor packaged in a suitable container. The
kit optionally further comprises an instruction set or user manual
detailing preferred methods of using the kit components for sensing
a substance of interest.
[0114] When used according to the instructions, the kit enables the
user to identify disease or condition specific substances (such as
sugars and/or fats and/or proteins and/or antigens) using patient
tissues, including, but not limited to interstitial fluids. The kit
can also allow the user to access a central database server that
receives and provides information to the user. Additionally, or
alternatively, the kit allows the user, e.g., a health care
practitioner, clinical laboratory, or researcher, to determine the
probability that an individual belongs to a clinically relevant
class of subjects (diagnostic or otherwise).
[0115] Embodiment in a Programmed Information Appliance
[0116] The invention may be embodied in whole or in part within the
circuitry of an application specific integrated circuit (ASIC) or a
programmable logic device (PLD). In such a case, the invention may
be embodied in a computer understandable descriptor language, which
may be used to create an ASIC, or PLD that operates as herein
described.
[0117] Integrated Systems
[0118] Integrated systems for the collection and analysis of
detection results, including detection or expression profiles,
molecular signatures, as well as for the compilation, storage and
access of the databases of the invention, typically include a
digital computer with software including an instruction set for
sequence searching and/or analysis, and, optionally, one or more of
high-throughput sample control software, image analysis software,
data interpretation software, a robotic control armature for
transferring solutions from a source to a destination (such as a
detection device) operably linked to the digital computer, an input
device (e.g., a computer keyboard) for entering subject data to the
digital computer, or to control analysis operations or high
throughput sample transfer by the robotic control armature.
Optionally, the integrated system further comprises an electronic
signal generator and detection scanner for probing a microarray.
The scanner can interface with analysis software to provide a
measurement of the presence or intensity of the hybridized and/or
bound suspected ligand.
[0119] Readily available computational hardware resources using
standard operating systems can be employed and modified according
to the teachings provided herein, e.g., a PC (Intel x86 or Pentium
chip-compatible DOS,.TM. OS2,.TM. WINDOWS,.TM. LINUX, or Macintosh,
Sun or PCs will suffice) for use in the integrated systems of the
invention. Current art in software technology is adequate to allow
implementation of the methods taught herein on a computer system.
Thus, in specific embodiments, the present invention can comprise a
set of logic instructions (either software, or hardware encoded
instructions) for performing one or more of the methods as taught
herein. For example, software for providing the described data
and/or statistical analysis can be constructed by one of skill
using a standard programming language such as Visual Basic,
Fortran, Basic, Java, or the like. Such software can also be
constructed utilizing a variety of statistical programming
languages, toolkits, or libraries.
[0120] FIG. 18 is a block diagram showing a representative example
logic device in which various aspects of the present invention may
be embodied. FIG. 18 shows an information appliance (or digital
device) 700 that may be understood as a logical apparatus that can
read instructions from media 717 and/or network port 719, which can
optionally be connected to server 720 having fixed media 722.
Apparatus 700 can thereafter use those instructions to direct
server or client logic, as understood in the art, to embody aspects
of the invention. One type of logical apparatus that may embody the
invention is a computer system as illustrated in 700, containing
CPU 707, optional input devices 709 and 711, disk drives 715 and
optional monitor 705. Fixed media 717, or fixed media 722 over port
719, may be used to program such a system and may represent a
disk-type optical or magnetic media, magnetic tape, solid state
dynamic or static memory, etc. In specific embodiments, the
invention may be embodied in whole or in part as software recorded
on this fixed media. Communication port 719 may also be used to
initially receive instructions that are used to program such a
system and may represent any type of communication connection.
[0121] Various programming methods and algorithms, including
genetic algorithms and neural networks, can be used to perform
aspects of the data collection, correlation, and storage functions,
as well as other desirable functions, as described herein. In
addition, digital or analog systems such as digital or analog
computer systems can control a variety of other functions such as
the display and/or control of input and output files. Software for
performing the electrical analysis methods of the invention are
also included in the computer systems of the invention.
[0122] Thus, a microneedle-based system according to specific
embodiments of the invention can be employed as an effective
glucose monitor using a microneedle array and dialysis. Due to the
optimum needle dimensions, it is sufficient to simply press the
system onto the skin in order to reach the desired location in the
epidermis with an abundant amount of interstitial fluid. The nerve
endings are located deeper in the skin so that this procedure is
painless. The glucose monitor can be attached to a skin location
(for example, with a self-adhesive, medical tape, a band, etc.) by
the patient himself without an assisted insertion procedure.
Other Embodiments
[0123] Although the present invention has been described in terms
of various specific embodiments, it is not intended that the
invention be limited to these embodiments. Modification within the
spirit of the invention will be apparent to those skilled in the
art. It is understood that the examples and embodiments described
herein are for illustrative purposes and that various modifications
or changes in light thereof will be suggested by the teachings
herein to persons skilled in the art and are to be included within
the spirit and purview of this application and scope of the
claims.
[0124] All publications, patents, and patent applications cited
herein or filed with this submission, including any references
filed as part of an Information Disclosure Statement, are
incorporated by reference in their entirety.
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