U.S. patent application number 11/388723 was filed with the patent office on 2006-11-23 for fluidic medical devices and uses thereof.
Invention is credited to Jeff Fenton, John Howard, Timothy M. Kemp, Ron Oral, Chris Todd, Shulin Zeng.
Application Number | 20060264779 11/388723 |
Document ID | / |
Family ID | 37397025 |
Filed Date | 2006-11-23 |
United States Patent
Application |
20060264779 |
Kind Code |
A1 |
Kemp; Timothy M. ; et
al. |
November 23, 2006 |
Fluidic medical devices and uses thereof
Abstract
This invention is in the field of medical devices. Specifically,
the present invention provides fluidic systems having a plurality
of reaction sites surrounded by optical barriers to reduce the
amount of optical cross-talk between signals detected from various
reaction sites. The invention also provides a method of
manufacturing fluidic systems and methods of using the systems.
Inventors: |
Kemp; Timothy M.; (San Jose,
CA) ; Todd; Chris; (San Jose, CA) ; Oral;
Ron; (Fremont, CA) ; Zeng; Shulin;
(Gaithersburg, MD) ; Howard; John; (Saratoga,
CA) ; Fenton; Jeff; (San Jose, CA) |
Correspondence
Address: |
WILSON SONSINI GOODRICH & ROSATI
650 PAGE MILL ROAD
PALO ALTO
CA
94304-1050
US
|
Family ID: |
37397025 |
Appl. No.: |
11/388723 |
Filed: |
March 24, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60678801 |
May 9, 2005 |
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60705489 |
Aug 5, 2005 |
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60717192 |
Sep 16, 2005 |
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60721097 |
Sep 28, 2005 |
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Current U.S.
Class: |
600/583 |
Current CPC
Class: |
B01L 2300/0867 20130101;
A61B 5/14546 20130101; A61B 5/150099 20130101; A61B 5/1427
20130101; B01L 2300/0887 20130101; B01L 2300/021 20130101; A61B
5/1411 20130101; Y10T 436/143333 20150115; A61B 5/14532 20130101;
B01L 2300/023 20130101; B01L 3/50273 20130101; G01N 33/53 20130101;
A61B 5/417 20130101; A61B 5/157 20130101; B01L 2300/044 20130101;
G01N 33/5302 20130101; A61B 5/412 20130101; Y10T 436/11 20150115;
A61B 5/150022 20130101; G01N 33/50 20130101; A61B 5/1495 20130101;
G01N 33/54386 20130101; G16H 40/63 20180101; B01L 2300/0877
20130101; Y10T 436/10 20150115; B01L 2300/087 20130101; B01L
2300/0883 20130101; A61B 5/150251 20130101; A61B 5/150763 20130101;
G01N 21/76 20130101; A61B 5/150854 20130101; B01L 2300/0636
20130101; A61B 5/15142 20130101; G01N 2500/00 20130101; Y02A 90/10
20180101; Y10T 436/12 20150115; B01L 2300/0816 20130101; Y10T
436/115831 20150115 |
Class at
Publication: |
600/583 |
International
Class: |
A61B 5/00 20060101
A61B005/00 |
Claims
1. An apparatus for detecting an analyte in a biological fluid of a
subject, comprising: a) a sample collection unit for introducing a
biological fluid in fluid communication with a plurality of
reaction sites; b) a plurality of reactant chambers carrying a
plurality of reactants in fluid communication with said reaction
sites, wherein said plurality of reaction sites comprise a
plurality of reactants bound thereto for detecting said analyte;
and c) a system of fluidic channels to allow said biological fluid
and said plurality of reactants to flow in said apparatus, wherein
at least one channel located between said plurality of reaction
sites comprises an optical barrier to reduce the amount of optical
cross-talk between said plurality of said reaction sites during
detection of said analyte.
2. The apparatus of claim 1, further comprising a plurality of
waste chambers in fluid communication with at least one of said
reaction sites.
3. The apparatus of claim 1 wherein each channel located between
said plurality of reaction sites comprises an optical barrier.
4. The apparatus of claim 1 wherein the biological fluid is less
than about 500 microliters.
5. The apparatus of claim 1 wherein said optical barrier comprises
a nonlinear fluidic channel.
6. The apparatus of claim 1 wherein the fluid is less than about 50
microliters.
7. The apparatus of claim 1, wherein the reactants comprise
immunoassay reagents.
8. The apparatus of claim 7, wherein said apparatus detects a
plurality of analytes, wherein the analytes are identified by
distinct signals detectable over a range of 3 orders of
magnitude.
9. The apparatus of claim 7, wherein the immunoassay reagents
detect a polypeptide glycoprotein, polysaccharide, lipid, nucleic
acid, and a combination thereof.
10. The apparatus of claim 7, wherein the immunoassay reagents
detect a member selected from the group consisting of drug, drug
metabolite, biomarker indicative of a disease, tissue specific
marker, and biomarker specific for a cell or cell type.
11. The apparatus of claim 1, wherein the detectable signal is a
luminescent signal.
12. An apparatus for detecting an analyte in a biological fluid of
a subject, comprising a) a sample collection unit for introducing a
biological fluid in fluid communication with a plurality of
reaction sites, wherein said plurality of reaction sites comprise a
plurality of bound reactants for detecting said analyte; b) a
plurality of reactant chambers carrying a plurality of reactants in
fluid communication with said reaction sites; and c) a system of
fluidic channels to allow said biological fluid and said plurality
of reactants to flow in said apparatus, wherein said bound
reactants in at least one reaction site are unevenly
distributed.
13. The apparatus of claim 12, wherein said bound reactants in the
at least one reaction site are localized around the center of said
reaction site.
14. The apparatus of claim 13, wherein an outer edge of the at
least one reaction site is at a distance sufficiently far from said
bound reactants to reduce signals unrelated to the presence of said
analyte.
15. The apparatus of claim 12, further comprising a waste chamber
in fluid communication with said reaction sites.
16. The apparatus of claim 14 wherein said unbound reactant is
coupled to said edge of said reaction site.
17. A method of manufacturing a fluidic device for detecting an
analyte in a biological fluid of a subject, comprising: a)
providing a plurality of layers of a fluidic device; b)
ultrasonically welding said layers together such that a fluidic
network exists between a sample collection unit, at least one
reactant chamber, at least one reaction site, and at least one
waste chamber.
18. The method of claim 17 wherein said at least one reaction
chamber is vacuum sealed.
19. The method of claim 17, wherein said fluidic device comprises a
system of fluidic channels to allow contact of said biological
fluid with reactants in said at least one reaction site.
20. The method of claim 17, wherein said reaction site comprises an
optical barrier to reduce the amount of optical cross-talk between
another reaction site on the fluidic device.
Description
CROSS-REFERENCE
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/678,801, filed May 9, 2005 and U.S. Provisional
Application No. 60/705,489, filed Aug. 5, 2005 and U.S. Provisional
Application No. 60/717,192, filed Sep. 16, 2005, and U.S.
Provisional Application No. 60/721,097, filed Sep. 28, 2005 which
are incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] Point-of-Care (POC) testing systems and fluidic devices or
cartridges are becoming more common because of the advancement in
microfabrication technology such as MEMS technology, which enables
the fabrication of reliable and inexpensive fluidic based
cartridges. Generally, such systems use microvalves, micropumps,
microneedles, etc. for moving the fluids through the fluidic
system. A common system contains a reagent reservoir, a mixing
chamber, an analytical chamber and waste chamber. Fluids must
therefore be moved from one chamber to another. Some challenges in
moving such fluids in a fluidic device include mixing the reagents
with the sample, and washing unbound reagents from a detection
site. One of the common challenges is washing the unbound
conjugates after the incubation period, particularly removing
conjugates that remain stuck to the edges of the reaction site
walls. U.S. Pat. No. 5,600,993 provides a good summary of such
exemplary problems.
[0003] Various approaches that have been described to cause fluid
movement in a fluidic device include electrical, osmotic, and
capillary. U.S. Pat. No. 6,440,725 describes different fluid motive
sources for moving liquids through the chambers. One such example
uses a fluid inside a sealed pouch wherein the fluid is converted
to gas by an electrical current. This action pressurizes and
expands the fluid pouch. This sealed pumping pouch, or e-pump, is
positioned against a reagent pouch and forces the contents of the
reagent pouch into the fluidic circuit as the pumping pouch
expands. The '725 patent also describes various other fluid motive
sources such as pressure or vacuum source, or using a solenoid or
stepper motor to provide a force to press against a reagent
pouch.
[0004] US Patent Application No. 20050130292 describes using
mechanical energy to move fluids within a fluidic device. In this
application the inventors describe minimal or no external power to
force the fluid through various chambers. A sample is loaded on to
a biochip and this biochip is inserted into a custom designed
socket. The work done in inserting the socket is converted to the
energy required for the fluidic flow. Subsequent steps of directing
the sample to the desired chamber, mixing it, and assaying it are,
according to the inventors, accomplished with minimal power
consumption. Such a device has several valves and pumps, even if
the pumps are not driven by external electrical energy, which are
difficult to include in a small disposable fluidic system.
[0005] Generally, reagents in a POC system are stored in a dry
state to improve shelf-like. Buffers are generally stored
separately until the assay is to be performed, at which time the
reagents are hydrated. However, dry reagents may become wet or
hydrated before they are intended to do so. Buffers may leak from
their holding areas and mix with the dry reagents. It may thus be
beneficial to keep the dry reagents in a dry state until the assay
is initiated.
[0006] Cartridge or fluidic based POC systems may handle small
volumes of fluids. Nanoliter or even picoliter amounts of fluids
are sometimes forced to flow within fluidic channels. Either during
the sample introduction or a venting process, there is a
substantial likelihood that a bubble will be introduced into the
microfluidics system. A bubble introduced into the system can cause
an inaccurate measurement if the bubble is located in the detection
site during the detection step.
[0007] Current fluidic devices may experience optical cross-talk
when there are multiple reaction sites adjacent to one another.
When assays with different luminescent intensities are run in
adjacent reaction wells or chambers, photons (representing the
signal generated) can travel from one well to others comprising the
accuracy of measurement from each well. The photons can travel
through construction materials of the wells and through the fluidic
channels that connect the wells. This problem may become worse the
longer the incubation time of the assay. Thus, there remains a
considerable need for new designs of fluidic cartridges with
reduced optical interference from adjacent reaction sites. The
present invention satisfies this need and provides related
advantages as well.
SUMMARY OF THE INVENTION
[0008] The present invention provides an apparatus for detecting an
analyte in a biological fluid of a subject. The apparatus comprises
a sample collection unit for introducing a biological fluid in
fluid communication with a plurality of reaction sites, a plurality
of reactant chambers carrying a plurality of reactants in fluid
communication with said reaction sites wherein said plurality of
reaction sites comprise a plurality of reactants bound thereto for
detecting said analyte, and a system of fluidic channels to allow
said biological fluid and said plurality of reactants to flow in
said apparatus, wherein at least one channel located between said
plurality of reaction sites comprises an optical barrier to reduce
the amount of optical cross-talk between said plurality of said
reaction sites during detection of said analyte.
[0009] In one aspect, the apparatus further comprising a plurality
of waste chambers in fluid communication with at least one of said
reaction sites. In another aspect, each channel located between
said plurality of reaction sites comprises an optical barrier.
[0010] The present invention also proivdes an apparatus for
detecting an analyte in a biological fluid of a subject comprises a
sample collection unit for introducing a biological fluid in fluid
communication with a plurality of reaction sites, wherein said
plurality of reaction sites comprise a plurality of bound reactants
for detecting said analyte, a plurality of reactant chambers
carrying a plurality of reactants in fluid communication with said
reaction sites, and a system of fluidic channels to allow said
biological fluid and said plurality of reactants to flow in said
apparatus wherein said bound reactants in at least one reaction
site are unevenly distributed.
[0011] The present invention further provides a method of
manufacturing a fluidic device for detecting an analyte in a
biological fluid of a subject. The method comprises providing a
plurality of layers of a fluidic device, and ultrasonically welding
said layers together such that a fluidic network exists between a
sample collection unit, at least one reactant chamber, at least one
reaction site, and at least one waste chamber.
INCORPORATION BY REFERENCE
[0012] All publications and patent applications mentioned in this
specification are herein incorporated by reference to the same
extent as if each individual publication or patent application was
specifically and individually indicated to be incorporated by
reference.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The novel features of the invention are set forth with
particularity in the appended claims. A better understanding of the
features and advantages of the present invention will be obtained
by reference to the following detailed description that sets forth
illustrative embodiments, in which the principles of the invention
are utilized, and the accompanying drawings of which:
[0014] FIG. 1 illustrates exemplary multiple components of the
present system.
[0015] FIG. 2 shows different layers of an exemplary fluidic device
prior to assembly.
[0016] FIGS. 3 and 4 illustrate the fluidic network within an
exemplary fluidic device.
[0017] FIG. 5 shows a top, side, and bottom view of exemplary
reagent chambers of the present invention.
[0018] FIG. 6 illustrates an exemplary side view of a reagent
chamber in fluidic communication with a fluidic device.
[0019] FIG. 7 illustrates exemplary reagent chambers being filled
with reagents.
[0020] FIGS. 8 and 9 illustrate a side view of an exemplary fluidic
device in combination with actuating elements of the reader
assembly.
[0021] FIG. 10 illustrates a two-step assay and a competitive
binding assay.
[0022] FIG. 11 shows an exemplary two-step chemiluminescence enzyme
immunoassay.
[0023] FIG. 12 illustrates the increased sensitivity of the
two-step chemiluminescence enzyme immunoassay.
[0024] FIGS. 13A-C illustrate exemplary fluidic channels between
reaction sites.
[0025] FIGS. 14A and 14B illustrate reaction sites to reduce the
signal from unbound conjugates remaining in reaction sites.
[0026] FIG. 15 shows an exemplary bubble trapper or remover to
prevent bubbles from entering the reaction sites.
DETAILED DESCRIPTION OF THE INVENTION
[0027] One aspect of the present invention is a system for
detecting an analyte in a sample of bodily fluid. The subject
system has one or more of the following components: a) a sample
collection unit for introducing a biological fluid in fluid
communication with a plurality of reaction sites, b) a plurality of
reactant chambers carrying a plurality of reactants in fluid
communication with said reaction sites wherein said plurality of
reaction sites comprise a plurality of reactants bound thereto for
detecting said analyte, and c) a system of fluidic channels to
allow said biological fluid and said plurality of reactants to flow
in said apparatus, wherein at least one channel located between
said plurality of reaction sites comprises an optical barrier to
reduce the amount of optical cross-talk between said plurality of
said reaction sites during detection of said analyte.
[0028] Where desired, the system may further comprise a reader
assembly and a communication assembly. The sample collection unit
typically allows a sample of bodily fluid collected from a subject
to react with reactants contained within the assay assembly for
generating a signal indicative of the presence of the analyte of
interest. The reader assembly detects the signal, which is then
transmitted via the communication assembly to an external device
for further processing.
[0029] Any bodily fluids suspected to contain an analyte of
interest can be used in conjunction with the subject system or
devices. Commonly employed bodily fluids include but are not
limited to blood, serum, saliva, urine, gastric and digestive
fluid, tears, stool, semen, vaginal fluid, interstitial fluids
derived from tumorous tissue, and cerebrospinal fluid. In a
preferred embodiment, the bodily fluids are used directly for
detecting the analytes present therein with the subject fluidic
device without further processing. Where desired, however, the
bodily fluids can be pre-treated before performing the analysis
with the subject fluidic devices. The choice of pre-treatments will
depend on the type of bodily fluid used and/or the nature of the
analyte under investigation. For instance, where the analyte is
present at low level in a sample of bodily fluid, the sample can be
concentrated via any conventional means to enrich the analyte.
Methods of concentrating an analyte include but are not limited to
drying, evaporation, centrifugation, sedimentation, precipitation,
and amplification. Where the analyte is a nucleic acid, it can be
extracted using various lytic enzymes or chemical solutions
according to the procedures set forth in Sambrook et al.
("Molecular Cloning: A Laboratory Manual"), or using nucleic acid
binding resins following the accompanying instructions provided by
manufactures. Where the analyte is a molecule present on or within
a cell, extraction can be performed using lysing agents including
but not limited to denaturing detergent such as SDS or
non-denaturing detergent such as thesit, sodium deoxylate, triton
X-100, and tween-20.
[0030] The volume of bodily fluid to be used with a fluidic device
of the present invention is generally less than about 500
microliters, typically between about 1 to 100 microliters. Where
desired, a sample of 1 to 50 microliters or 1 to 10 microliters can
be used for detecting an analyte using the subject fluidic
device.
[0031] A bodily fluid may be drawn from a patient and brought into
the fluidic device in a variety of ways, including but not limited
to, lancing, injection, or pipetting. In one embodiment, a lancet
punctures the skin and draws the sample into the fluidic device
using, for example, gravity, capillary action, aspiration, or
vacuum force. The lancet may be part of the fluidic device, or part
of a reader assembly, or as a stand alone component. Where needed,
the lancet may be activated by a variety of mechanical, electrical,
electromechanical, or any other known activation mechanism or any
combination of such methods. In another embodiment where no active
mechanism is required, a patient can simply provide a bodily fluid
to the fluidic device, as for example, could occur with a saliva
sample. The collected fluid can be placed in the sample collection
unit within the fluidic device. In yet another embodiment, the
fluidic device comprises at least one microneedle which punctures
the skin. The microneedle can be used with a fluidic device alone,
or can puncture the skin after the fluidic device is inserted into
a reader assembly.
[0032] In some embodiments a microneedle is about the size of a
human hair and has an integrated microreservoir or cuvette. The
microneedle may painlessly penetrate the skin and draw a small
blood sample. More preferably, the microneedle collects about 0.01
to about 1 microliter, preferably about 0.05 to about 0.5
microliters and more preferably about 0.1 to about 0.3 microliters
of capillary blood. In some embodiments a microneedle may be
constructed out of silicon and is about 10 to about 200 microns in
diameter, preferably about 50 to about 150 microns in diameter, and
most preferably about 100 microns in diameter, making their
application to the skin virtually painless. To ensure that a
capillary is actually struck by a needle, a plurality of
microneedles may be used for sample collection. Such microneedles
may be of the type marketed by Pelikan (Palo Alto, Calif.) and/or
Kumetrix (Union City, Calif.). U.S. Pat. No. 6,503,231 discloses
microneedles which may be used with the present invention.
[0033] Microfabrication processes that may be used in making the
microneedles disclosed herein include without limitation
lithography; etching techniques such as wet chemical, dry, and
photoresist removal; thermal oxidation of silicon; electroplating
and electroless plating; diffusion processes such as boron,
phosphorus, arsenic, and antimony diffusion; ion implantation; film
deposition such as evaporation (filament, electron beam, flash, and
shadowing and step coverage), sputtering, chemical vapor deposition
(CVD), epitaxy (vapor phase, liquid phase, and molecular beam),
electroplating, screen printing, and lamination. See generally
Jaeger, Introduction to Microelectronic Fabrication (Addison-Wesley
Publishing Co., Reading Mass. 1988); Runyan, et al., Semiconductor
Integrated Circuit Processing Technology (Addison-Wesley Publishing
Co., Reading Mass. 1990); Proceedings of the IEEE Micro Electro
Mechanical Systems Conference 1987-1998; Rai-Choudhury, ed.,
Handbook of Microlithography, Micromachining & Microfabrication
(SPIE Optical Engineering Press, Bellingham, Wash. 1997).
Alternatively, microneedles may be molded in silicon wafers and
then plated using conventional wire cutting techniques with nickel,
gold, titanium or various other biocompatible metals. In some
embodiments microneedles can be fashioned from biopolymers. In some
embodiments microneedles may be fabricated and employed for the
claimed devices according to the methods of Mukerjee et al.,
Sensors and Actuators A: Physical, Volume 114, Issues 2-3, 1 Sep.
2004, Pages 267-275.
[0034] In preferred embodiments a microneedle is only used once and
then discarded. In some embodiments a mechanical actuator can
insert and withdraw the microneedle from the patient, discard the
used needle, and reload a new microneedle. The mechanical
technologies developed and manufactured in very high volumes for
very small disk drives have a similar set of motion and low cost
requirements. In preferred embodiments the actuator is a MEMS
(micro machined electromechanical system) device fabricated using
semiconductor-like batch processes. Such actuators include without
limitation nickel titanium alloy, neumatic, or piezo electric
devices. In some embodiments the microneedles are about 1 micron to
about 10 microns in thickness, preferably about 2 microns to about
6 microns in thickness, and most preferably about 4 microns in
thickness. In some embodiments the microneedles are about 10
microns to about 100 microns in height, preferably about 30 microns
to about 60 microns in height, and most preferably about 40 microns
in height.
[0035] FIG. 1 illustrates an exemplary system of the present
invention. As illustrated, a fluidic device provides a bodily fluid
from a patient and can be inserted into a reader assembly. The
fluidic device may take a variety of configurations and in some
embodiments the fluidic device may be in the form of a cartridge.
An identifier (ID) detector may detect an identifier on the fluidic
device. The identifier detector communicates with a communication
assembly via a controller which transmits the identifier to an
external device. Where desired, the external device sends a
protocol stored on the external device to the communication
assembly based on the identifier. The protocol to be run on the
fluidic device may comprise instructions to the controller of the
reader assembly to perform the protocol on the fluidic device,
including but not limited to a particular assay to be run and a
detection method to be performed. Once the assay is performed on
the fluidic device, a signal indicative of an analyte in the bodily
fluid sample is generated and detected by a detection assembly. The
detected signal may then be communicated to the communications
assembly, where it can be transmitted to the external device for
processing, including without limitation, calculation of the
analyte concentration in the sample.
[0036] FIG. 2 illustrates exemplary layers of a fluidic device
according to the present invention prior to assembly of the fluidic
device which is disclosed in more detail below. FIGS. 3 and 4
illustrate the fluidic network within an exemplary fluidic device.
The different layers are designed and assembled to form a three
dimensional fluidic channel network. A sample collection unit 4
provides a sample of bodily fluid from a patient. As will be
explained in further detail below a reader assembly comprises
actuating elements (not shown) can actuate the fluidic device to
start and direct the flow of a bodily fluid sample and assay
reagents in the fluidic device. In some embodiments actuating
elements first cause the flow of sample in the fluidic device 2
from sample collection unit 4 to reaction sites 6, move the sample
upward in the fluidic device from point G' to point G, and then to
waste chamber 8. The actuating elements then initiate the flow of
reagents from reagent chambers 10 to point B', point C', and point
D', then upward to points B, C, and D, respectively. The reagents
then move to point A, down to point A', and then to waste chamber 8
in a manner similar to the sample.
[0037] A sample collection unit 4 in a fluidic device 2 may provide
a bodily fluid sample from a patient by any of the methods
described above. If necessary, the sample may first be processed by
diluting the bodily fluid in a dilution chamber, and or may be
filtered by separating the plasma from the red blood cells in a
filtration chamber. In some embodiments the sample collection unit,
diluting chamber, and filtration chamber may be the same component,
and in some embodiments they may be different components, or any
two may be the same component and the other may be a separate
component. In some embodiments there may be more than one sample
collection unit in the fluidic device.
[0038] In some embodiments it may be desirable to detect the
presence of analytes on a cell surface, within a cell membrane, or
inside a cell. The difficulty of detecting such analytes is that
cells and other formed elements are particulate and components of
cells do not readily interact with traditional assay chemistries
which are designed to operate on analytes in solution. Cell-surface
analytes react slowly and inefficiently with surface bound probes,
and analytes inside the cell can not react at all with bound
probes. To allow the detection of such analytes, in some
embodiments the fluidic device may include a lysing assembly to
lyse cells present in the bodily fluid sample. The lysing assembly
may be incorporated with the sample collection unit, a dilution
chamber, and/or a filtration chamber. In some embodiments the
sample collection unit, dilution chamber, and lysing component are
within the same element in the fluidic device. In some embodiments
the lysing component may be incorporated with an assay reagent
described below.
[0039] Where desired, lysing agents may be impregnated and then
dried into porous mats, glass fiber mats, sintered frits or
particles such as Porex, paper, or other similar material. Lysing
agents may be dried onto flat surfaces. Lysing agents may also be
dissolved in liquid diluents or other liquid reagents. In preferred
embodiments porous materials are used to store the lysing agents
because they can store a lysing agent in dry form likely to be very
stable. They also facilitate the mixing of the bodily fluid sample
with the lysing agent by providing a tortuous path for the sample
as it moves through the porous material. In preferred embodiments
such porous materials have a disc shape with a diameter greater
than its thickness. In some embodiments lysing agents may be dried
onto porous materials using lyophilization, passive evaporation,
exposure to warm dry flowing gas, or other known methods.
[0040] A variety of lysing agents are available in the art and are
suitable for use in connection with the subject fluidic device.
Preferred lysing agents are non-denaturing, such as non-denaturing
detergents. Non-limiting examples of non-denaturing detergents
include thesit, sodium deoxylate, triton X-100, and tween-20. The
agents are preferably non-volatile in embodiments where the agents
are impregnated into a solid porous materials. In some embodiments
lysing agents are mixed together. Other materials may be mixed with
the lysing agents to modify the lytic effects. Such exemplary
materials may be, without limitation, buffers, salts, and proteins.
In preferred embodiments lysing agents will be used in amounts that
are in excess of the minimum amount required to lyse cells. In some
embodiments lysing agents will be used that can lyse both white and
red cells.
[0041] One of the advantages of the present invention is that any
reagents necessary to perform an assay on a fluidic device
according to the present invention are preferably on-board, or
housed within the fluidic device before, during, and after the
assay. In this way the only inlet or outlet from the fluidic device
is preferably the bodily fluid sample initially provided by the
fluidic device. This design also helps create an easily disposable
fluidic device where all fluids or liquids remain in the device.
The on-board design also prevents leakage from the fluidic device
into the reader assembly which should remain free from
contamination from the fluidic device.
[0042] In a preferred embodiment there is at least one reagent
chamber. In some embodiments there may be two, three, four, five,
six, or more, or any number of reagent chambers as are necessary to
fulfill the purposes of the invention. A reagent chamber is
preferably in fluid communication with at least one reaction site,
and when the fluidic device is actuated as described herein,
reagents contained in said reagent chambers are released into the
fluidic channels within the fluidic device.
[0043] Reagents according to the present invention include without
limitation wash buffers, enzyme substrates, dilution buffers,
conjugates, enzyme-labeled conjugates, DNA amplifiers, sample
diluents, wash solutions, sample pre-treatment reagents including
additives such as detergents, polymers, chelating agents,
albumin-binding reagents, enzyme inhibitors, enzymes,
anticoagulants, red-cell agglutinating agents, antibodies, or other
materials necessary to run an assay on a fluidic device. An enzyme
conjugate can be either a polyclonal antibody or monoclonal
antibody labeled with an enzyme that can yield a detectable signal
upon reaction with an appropriate substrate. Non-limiting examples
of such enzymes are alkaline phosphatase and horseradish
peroxidase. In some embodiments the reagents comprise immunoassay
reagents.
[0044] In some embodiments a reagent chamber contains approximately
about 50 .mu.l to about 1 ml of fluid. In some embodiments the
chamber may contain about 100 .mu.l of fluid. The volume of liquid
in a reagent chamber may vary depending on the type of assay being
run or the sample of bodily fluid provided. In some embodiments the
reagents are initially stored dry and liquified upon initiation of
the assay being run on the fluidic device.
[0045] In a preferred embodiment there is at least one reagent
chamber. In some embodiments there may be two, three, four, five,
six, or more, or any number of reagent chambers as are necessary to
fulfill the purposes of the invention. A reagent chamber is
preferably in fluid communication with at least one reaction site,
and when the fluidic device is actuated as described herein,
reagents contained in said reagent chambers are released into the
fluidic channels within the fluidic device.
[0046] Reagents according to the present invention include without
limitation wash buffers, substrates, dilution buffers, conjugates,
enzyme-labeled conjugates, DNA amplifiers, sample diluents, wash
solutions, sample pre-treatment reagents including additives such
as detergents, polymers, chelating agents, albumin-binding
reagents, enzyme inhibitors, enzymes, anticoagulants, red-cell
agglutinating agents, antibodies or other materials necessary to
run an assay on a fluidic device. An enzyme conjugate can be either
a polyclonal antibody or monoclonal antibody labeled with an
enzyme, such as alkaline phosphatase or horseradish peroxidase. In
some embodiments the reagents are immunoassay reagents.
[0047] In some embodiments a reagent chamber contains approximately
about 50 .mu.l to about 1 ml of fluid. In some embodiments the
chamber may contain about 100 .mu.l of fluid. The volume of liquid
in a reagent chamber may vary depending on the type of assay being
run or the sample of bodily fluid provided. In some embodiments the
reagents are initially stored dry and liquified upon initiation of
the assay being run on the fluidic device.
[0048] FIG. 5 illustrate a different embodiment of a sealed reagent
chamber. FIG. 5 shows a top, side, and bottom view of a reagent
chamber. A top layer 11 contains a plurality of bubbles or pouches
13. A bottom layer 15 has a bottom surface that is bonded to the
fluidic device base 17 as shown in FIG. 6. The bottom layer 15 has
a plurality of fluidic channels 19 dispersed through the entire
surface, where each channel traverses the bottom layer 15. The
fluid in the reagent chamber is contained within the chamber by
pressure burstable seal 21 between the fluidic channel 19 and the
chamber 13. The burstable seal 21 is designed such that at a
pre-determined pressure the seal bursts allowing the fluid in the
chamber 13 to flow out into a fluidic channel 19.
[0049] FIG. 7 shows an exemplary process of filling the reagent
chambers 13 with, for example, reagents. Reagent chambers 13 may be
filled with fluid using a fill channel and a vacuum draw channel.
The process of filling the reagents involves first removing all the
air from the chamber. This is done by drawing a vacuum through the
vacuum draw channel. Once the vacuum is drawn, a permanent seal is
placed between the fill channel and the vacuum draw channel. Next,
required reagents are dispensed into the chamber through the fill
channel. Then, a permanent seal is placed between the chamber and
the fill channel. This ensures that when the chamber is compressed,
the fluid can flow in only one direction, towards the burstable
seal. If the compression imparts a pressure larger than the burst
pressure of seal, the seal bursts and the fluid flows into the
fluidic channel.
[0050] FIGS. 8 and 9 illustrate an embodiment of a fluidic device
in operation with actuating elements as described herein. Fluidic
device 2 contains a reagent chamber 10 and a layer of burstable
foil 12 enclosing the reagent chamber. Above the burstable foil 12
is a portion of the microfluidic circuit 14. A tough, but
elastomeric top cover 16 acts as the top layer of the fluidic
device 2. The reader assembly includes a valve actuation plate 18.
Securely attached to the plate 18 is a non-coring needle 20 such
that when the plate is lowered, the sharp edge of the needle
contacts the elastomeric cover 16. The top cover could also be made
of flexible silicone material that would act as a moisture
impermeable seal. This embodiment also provides a solution to
liquid evaporation and leakage from a fluidic device by isolating
any liquid reagents in the fluidic device from any dry reagents
until the assay is initiated.
[0051] In preferred embodiments the reagent chamber and sample
collection unit are fluidly connected to reaction sites where bound
reactant can detect an analyte of interest in the bodily fluid
sample using the assay. A reaction site could then provide a signal
indicative of the presence of the analyte of interest, which can
then be detected by a detection device described in detail herein
below.
[0052] In some embodiments the reactions sites are flat but they
may take on a variety of alternative surface configurations. The
reaction site preferably forms a rigid support on which a reactant
can be immobilized. The reaction site surface is also chosen to
provide appropriate light-absorbing characteristics. For instance,
the reaction site may be functionalized glass, Si, Ge, GaAs, GaP,
SiO.sub.2, SiN.sub.4, modified silicon, or any one of a wide
variety of gels or polymers such as (poly)tetrafluoroethylene,
(poly)vinylidenedifluoride, polystyrene, polycarbonate,
polypropylene, or combinations thereof. Other appropriate materials
may be used in accordance with the present invention.
[0053] A reactant immobilized at a reaction site can be anything
useful for detecting an analyte of interest in a sample of bodily
fluid. For instance, such reactants include without limitation
nucleic acid probes, antibodies, cell membrane receptors,
monoclonal antibodies and antisera reactive with a specific
analyte. Various commercially available reactants such as a host of
polyclonal and monoclonal antibodies specifically developed for
specific analytes can be used.
[0054] One skilled in the art will appreciate that there are many
ways of immobilizing various reactants onto a support where
reaction can take place. The immobilization may be covalent or
noncovalent, via a linker moiety, or tethering them to an
immobilized moiety. These methods are well known in the field of
solid phase synthesis and micro-arrays (Beier et al., Nucleic Acids
Res. 27:1970-1-977 (1999). Non-limiting exemplary binding moieties
for attaching either nucleic acids or proteinaceous molecules such
as antibodies to a solid support include streptavidin or
avidin/biotin linkages, carbamate linkages, ester linkages, amide,
thiolester, (N)-functionalized thiourea, functionalized maleimide,
amino, disulfide, amide, hydrazone linkages, and among others. In
addition, a silyl moiety can be attached to a nucleic acid directly
to a substrate such as glass using methods known in the art.
[0055] In some embodiments there are more than one reaction sites
which can allow for detection of multiple analytes of interest from
the same sample of bodily fluid. In some embodiments there are two,
three, four, five, six, or more reaction sites, or any other number
of reaction sites as may be necessary to carry out the intent of
the invention.
[0056] In embodiments with multiple reaction sites on a fluidic
device, each reaction site may contain a probe different from a
probe on a different reaction site. In a fluidic device with, for
example, three reaction sites, there may be three different probes,
each bound to a different reaction site to bind to three different
analytes of interest in the sample. In some embodiments there may
be different probes bound to a single reaction site if, for
example, a CCD with multiple detection areas were used as the
detection device, such that multiple different analytes could be
detected in a single reaction site. The capability to use multiple
reaction sites in addition to multiple different probes on each
reaction site enables the high-throughput characteristics of the
present invention.
[0057] The present invention allows for the detection of multiple
analytes on the same fluidic device. If assays with different
luminescent intensities are run in adjacent reaction sites, photons
(signals that emanate from the reactions) may travel from one
reaction site to an adjacent reaction site, as reaction sites may
be constructed of materials that allow photons to travel through
the fluidic channels that connect the sites. This optical cross
talk may compromise the accuracy of the detected photons. FIGS. 13B
and 13C illustrate different embodiments of this invention that can
eliminate or reduce the amount of optical cross-talk. Non-linear
channels 22 will not allow photons (light) to pass through. Hence,
embodiments such as those shown in FIGS. 13B and 13C would not
allow signals from a reaction site to contaminate a signal produced
from an adjacent site from which a detection device may be
detecting. Additionally, the edges or walls of a reaction site may
be constructed using optically opaque materials so that light will
not escape the wells. In some embodiments the reaction sites are
white or opaque.
[0058] In one exemplary configuration, the bound reactants in the
at least one reaction site are localized around the center of said
reaction site. In another exemplary configuration, an outer edge of
the at least one reaction site is at a distance sufficiently far
from said bound reactants to reduce signals unrelated to the
presence of said analyte. Distancing the edge of the reaction site
from the center area where bound reactants are concentrated allows
reduction of interfering signals from the background that does not
relate to the presence of the analyte of interest.
[0059] At least one of these channels will typically have small
cross sectional dimensions. In some embodiments the dimensions are
from about 0.01 mm to about 5 mm, preferably from about 0.03 mm to
about 3 mm, and more preferably from about 0.05 mm to about 2 mm.
Fluidic channels in the fluidic device may be created by, for
example without limitation, precision injection molding, laser
etching, or any other technique known in the art to carry out the
intent of the invention.
[0060] One of the common problems encountered in a microfluidic
based assay system is the presence of air or gas bubbles. It is
extremely difficult to remove a bubble once it is trapped within a
fluidic channel. Bubbles present anywhere in the fluidic circuit,
particularly in the reaction sites can compromise the assay
capabilities. A bubble may end up occupying part of all of the
surface area of a reaction site. Consequently the reader may end up
reading a muted signal or no signal at all. FIG. 15 illustrates an
embodiment where a bubble could be trapped in a filter 28 before it
reaches a reaction site 6. A bubble trapper 28 can be positioned
between a sample collection unit 4 and reaction site 6. The bubble
trapper can have such a geometry that the bubbles tend to migrate
towards the edges of this surface and remain stuck at that service,
thereby not entering into the reaction sites.
[0061] Manufacturing of the fluidic channels may generally be
carried out by any number of microfabrication techniques that are
well known in the art. For example, lithographic techniques are
optionally employed in fabricating, for example, glass, quartz or
silicon substrates, using methods well known in the semiconductor
manufacturing industries such as photolithographic etching, plasma
etching or wet chemical etching. Alternatively, micromachining
methods such as laser drilling, micromilling and the like are
optionally employed. Similarly, for polymeric substrates, well
known manufacturing techniques may also be used. These techniques
include injection molding or stamp molding methods where large
numbers of substrates are optionally produced using, for example,
rolling stamps to produce large sheets of microscale substrates or
polymer microcasting techniques where the substrate is polymerized
within a micromachined mold.
[0062] In some embodiments at least one of the different layers of
the fluidic device may be constructed of polymeric substrates. Non
limiting examples of polymeric materials include polystyrene,
polycarbonate, polypropylene, polydimethysiloxanes (PDMS),
polyurethane, polyvinylchloride (PVC), and polysulfone.
[0063] The fluidic device may be manufactured by stamping, thermal
bonding, adhesives or, in the case of certain substrates, for
example, glass, or semi-rigid and non-rigid polymeric substrates, a
natural adhesion between the two components. In some embodiments
the fluidic device is manufactured by ultrasonic or acoustic
welding.
[0064] FIG. 2 shows one embodiment of the invention in which
fluidic device 2 is comprised of seven layers. Features as shown
are, for example, cut in the polymeric substrate such that when the
layers are properly positioned when assembly will form a fluidic
network. In some embodiments more or fewer layers may be used to
construct a fluidic device to carry out the purpose of the
invention.
[0065] One goal of the present invention is to prevent fluid inside
a fluidic device from contacting the components of a reader
assembly which may need to remain dry and or uncontaminated, and
also to prevent contamination to a detection device within the
reader assembly. A leak in the fluidic device could result in
liquids, for example reagents or waste, escaping from the fluidic
device and contaminating the reader. In other embodiments a liquid
absorbing material, such as polymeric materials found in diapers,
could be placed within a portion of the fluidic channel or waste
chamber to absorb the waste liquid. A non-limiting example of such
a polymer is sodium polyacrylate. Such polymers can absorb fluids
hundreds of times their weight. Hence, only minute quantities of
such polymeric materials may be required to accomplish the goal of
absorbing leaked fluids. In some embodiments a waste chamber is
filled with a superabsorbent material. In some embodiments leaked
liquid may be converted into a gel or other solid or semi-solid
form.
[0066] FIGS. 8 and 9 illustrate an exemplary sequence to initiate
the flow of a reagent within the fluidic device. An actuation plate
18 in the reader assembly comprises a non-coring needle or pin 20
which when lowered flexes the top cover 16, as it is preferably
made of strong, flexible elastomeric material. However, the easily
rupturable foil 12 then ruptures due to the stress induced by the
flexing of top cover 16. Valves located downstream to the reagent
chamber puncture different areas of foil in the fluidic device and
can then work in tandem with a pump within the reader assembly to
create a vacuum force to pull the reagent out of the reagent
chamber 6 into a fluidic channel and then direct the flow of the
reagent to a reaction site. At least one valve is preferably
fluidically connected to a pump housed within the reader assembly.
The non-coring needle or pin 20 is removed from the fluidic device
when the device is removed from the reader assembly. One of the
advantages of this embodiment is that no on-chip pump is required,
which, at least, decreases the size and cost of the fluidic device,
and allows the device to be disposable.
[0067] In some embodiments a method of manufacturing a fluidic
device for detecting an analyte in a biological fluid of a subject
comprises providing a plurality of layers of a material, wherein at
least one of said layers comprises a sample collection unit,
wherein at least one of said layers comprises a filtration site,
wherein at least one of said layers comprises a reactant chamber,
wherein at least one of said layers comprises a fluidic channel,
wherein at least one of said layers comprises a reaction site,
wherein at least one of said layers comprises a waste chamber; and
ultrasonically welding said layers together such that a fluidic
network of channels exists between said sample collection unit,
said reactant chambers, said filtration site, said reaction sites,
said fluidic channel, and said waste chamber.
[0068] In preferred embodiments the different layers of the fluidic
device are ultrasonically welded together according to methods
known in the art. The layers may also be coupled together using
other methods, including without limitation stamping, thermal
bonding, adhesives or, in the case of certain substrates, for
example, glass, or semi-rigid and non-rigid polymeric substrates, a
natural adhesion between the two components
[0069] The subject system provides an effective means for high
throughput and real-time detection of analytes present in a bodily
fluid from a subject. The detection methods may be used in a wide
variety of circumstances including identification and
quantification of analytes that are associated with specific
biological processes, physiological conditions, disorders or stages
of disorders. As such, the subject apparatus and systems have a
broad spectrum of utility in, e.g. drug screening, disease
diagnosis, phylogenetic classification, parental and forensic
identification. The subject apparatus and systems are also
particularly useful for advancing preclinical and clinical stage of
development of therapeutics, improving patient compliance,
monitoring ADRs associated with a prescribed drug, and developing
individualized medicine.
[0070] As used herein, the term "subject" or "patient" is used
interchangeably herein, which refers to a vertebrate, preferably a
mammal, more preferably a human. Mammals include, but are not
limited to, murines, simians, humans, farm animals, sport animals,
and pets.
[0071] In some embodiments a sample of bodily fluid can first be
provided to the fluidic device by any of the methods described
herein. The fluidic device can then be inserted into the reader
assembly. An identification detector housed within the reader
assembly can detect an identifier of the fludic device and
communicate the identifier to a communication assembly, which is
preferably housed within the reader assembly. The communication
assembly then transmits the identifier to an external device which
transmits a protocol to run on the fluidic device based on the
identifier to the communication assembly. A controller preferably
housed within the reader assembly controls actuating elements
including at least one pump and one valve which interact with the
fluidic device to control and direct fluid movement within the
device. In some embodiments the fist step of the assay is a wash
cycle where all the surfaces within the fluidic device are wetted
using a wash buffer. The fluidic device is then calibrated using a
calibration assembly by running the same reagents as will be used
in the assay through the calibration reaction sites, and then a
luminescence signal from the reactions sites is detected by the
detection means, and the signal is used in calibrating the fluidic
device. The sample containing the analyte is introduced into the
fluidic channel. The sample may be diluted and further separated
into plasma or other desired component at a filter. The separated
sample now flows through the reaction sites and analytes present
therein will bind to reactants bound thereon. The plasma of sample
fluid is then flushed out of the reaction wells into a waste
chamber. Depending on the assay being run, appropriate reagents are
directed through the reaction sites to carry out the assay. All the
wash buffers and other reagents used in the various steps,
including the calibration step, are collected in wash tanks. The
signal produced in the reaction sites is then detected by any of
the methods described herein.
[0072] The term "analytes" according to the present invention
includes without limitation drugs, prodrugs, pharmaceutical agents,
drug metabolites, biomarkers such as expressed proteins and cell
markers, antibodies, serum proteins, cholesterol, polysaccharides,
nulceic acids, biological analytes, biomarker, gene, protein, or
hormone, or any combination thereof. At a molecular level, the
analytes can be polypeptide glycoprotein, polysaccharide, lipid,
nucleic acid, and a combination thereof.
[0073] Of particular interest are biomarkers are associated with a
particular disease or with a specific disease stage. Such analytes
include but are not limited to those associated with autoimmune
diseases, obesity, hypertension, diabetes, neuronal and/or muscular
degenerative diseases, cardiac diseases, endocrine disorders, any
combinations thereof.
[0074] Of also interest are biomarkers that are present in varying
abundance in one or more of the body tissues (i.e.,
tissue-specific) including heart, liver, prostate, lung, kidney,
bone marrow, blood, skin, bladder, brain, muscles, nerves, and
selected tissues that are affected by various disease, such as
different types of cancer (malignant or non-metastatic), autoimmune
diseases, inflammatory or degenerative diseases.
[0075] Also of interest are analytes that are indicative of a
microorganism. Exemplary microorganisms include but are not limited
to bacterium, virus, fungus and protozoa. Analytes that can be
detected by the subject method also include blood-born pathogens
selected from a non-limiting group that consists of Staphylococcus
epidermidis, Escherichia coli, methicillin-resistant Staphylococcus
aureus (MSRA), Staphylococcus aureus, Staphylococcus hominis,
Enterococcus faecalis, Pseudomonas aeruginosa, Staphylococcus
capitis, Staphylococcus warneri, Klebsiella pneumoniae, Haemophilus
influnzae, Staphylococcus simulans, Streptococcus pneumoniae and
Candida albicans.
[0076] Analytes that can be detected by the subject method also
encompass a variety of sexually transmitted diseases selected from
the following: gonorrhea (Neisseria gorrhoeae), syphilis (Treponena
pallidum), clamydia (Clamyda tracomitis), nongonococcal urethritis
(Ureaplasm urealyticum), yeast infection (Candida albicans),
chancroid (Haemophilus ducreyi), trichomoniasis (Trichomonas
vaginalis), genital herpes (HSV type I & II), HIV I, HIV II and
hepatitis A, B, C, G, as well as hepatitis caused by TTV.
[0077] Additional analytes that can be detected by the subject
methods encompass a diversity of respiratory pathogens including
but not limited to Pseudomonas aeruginosa, methicillin-resistant
Staphlococccus aureus (MSRA), Klebsiella pneumoniae, Haemophilis
influenzae, Staphlococcus aureus, Stenotrophomonas maltophilia,
Haemophilis parainfluenzae, Escherichia coli, Enterococcus
faecalis, Serratia marcescens, Haemophilis parahaemolyticus,
Enterococcus cloacae, Candida albicans, Moraxiella catarrhalis,
Streptococcus pneumoniae, Citrobacter freundii, Enterococcus
faecium, Klebsella oxytoca, Pseudomonas fluorscens, Neiseria
meningitidis, Streptococcus pyogenes, Pneumocystis carinii,
Klebsella pneumoniae Legionella pneumophila, Mycoplasma pneumoniae,
and Mycobacterium tuberculosis.
[0078] A variety of assays may be performed on a fluidic device
according to the present invention to detect an analyte of interest
in a sample. A wide diversity of labels are available in the art
that can be employed for conducting the subject assays. In some
embodiments labels are detectable by spectroscopic, photochemical,
biochemical, immunochemical, or chemical means. For example, useful
nucleic acid labels include 32P, 35S, fluorescent dyes,
electron-dense reagents, enzymes, biotin, dioxigenin, or haptens
and proteins for which antisera or monoclonal antibodies are
available. A wide variety of labels suitable for labeling
biological components are known and are reported extensively in
both the scientific and patent literature, and are generally
applicable to the present invention for the labeling of biological
components. Suitable labels include radionucleotides, enzymes,
substrates, cofactors, inhibitors, fluorescent moieties,
chemiluminescent moieties, bioluminescent labels, calorimetric
labels, or magnetic particles. Labeling agents optionally include,
for example, monoclonal antibodies, polyclonal antibodies,
proteins, or other polymers such as affinity matrices,
carbohydrates or lipids. Detection proceeds by any of a variety of
known methods, including spectrophotometric or optical tracking of
radioactive or fluorescent markers, or other methods which track a
molecule based upon size, charge or affinity. A detectable moiety
can be of any material having a detectable physical or chemical
property. Such detectable labels have been well-developed in the
field of gel electrophoresis, column chromatograpy, solid
substrates, spectroscopic techniques, and the like, and in general,
labels useful in such methods can be applied to the present
invention. Thus, a label includes without limitation any
composition detectable by spectroscopic, photochemical,
biochemical, immunochemical, electrical, optical thermal, or
chemical means.
[0079] In some embodiments the label is coupled directly or
indirectly to a molecule to be detected such as a product,
substrate, or enzyme, according to methods well known in the art.
As indicated above, a wide variety of labels are used, with the
choice of label depending on the sensitivity required, ease of
conjugation of the compound, stability requirements, available
instrumentation, and disposal provisions. Non radioactive labels
are often attached by indirect means. Generally, a ligand molecule
is covalently bound to a polymer. The ligand then binds to an
anti-ligand molecule which is either inherently detectable or
covalently bound to a signal system, such as a detectable enzyme, a
fluorescent compound, or a chemiluminescent compound. A number of
ligands and anti-ligands can be used. Where a ligand has a natural
anti-ligand, for example, biotin, thyroxine, and cortisol, it can
be used in conjunction with labeled, anti-ligands. Alternatively,
any haptenic or antigenic compound can be used in combination with
an antibody.
[0080] In some embodiments the label can also be conjugated
directly to signal generating compounds, for example, by
conjugation with an enzyme or fluorophore. Enzymes of interest as
labels will primarily be hydrolases, particularly phosphatases,
esterases and glycosidases, or oxidoreductases, particularly
peroxidases. Fluorescent compounds include fluorescein and its
derivatives, rhodamine and its derivatives, dansyl, and
umbelliferone. Chemiluminescent compounds include luciferin, and
2,3-dihydrophthalazinediones, such as luminol.
[0081] Methods of detecting labels are well known to those of skill
in the art. Thus, for example, where the label is a radioactive
label, means for detection include a scintillation counter or
photographic film as in autoradiography. Where the label is a
fluorescent label, it may be detected by exciting the fluorochrome
with the appropriate wavelength of light and detecting the
resulting fluorescence by, for example, microscopy, visual
inspection, via photographic film, by the use of electronic
detectors such as digital cameras, charge coupled devices (CCDs) or
photomultipliers and phototubes, or other detection device.
Similarly, enzymatic labels are detected by providing appropriate
substrates for the enzyme and detecting the resulting reaction
product. Finally, simple colorimetric labels are often detected
simply by observing the color associated with the label. For
example, conjugated gold often appears pink, while various
conjugated beads appear the color of the bead.
[0082] In some embodiments the detectable signal may be provided by
luminescence sources. "Luminescence" is the term commonly used to
refer to the emission of light from a substance for any reason
other than a rise in its temperature. In general, atoms or
molecules emit photons of electromagnetic energy (e.g., light) when
then move from an "excited state" to a lower energy state (usually
the ground state); this process is often referred to as
"radioactive decay". There are many causes of excitation. If
exciting cause is a photon, the luminescence process is referred to
as "photoluminescence". If the exciting cause is an electron, the
luminescence process is referred to as "electroluminescence". More
specifically, electroluminescence results from the direct injection
and removal of electrons to form an electron-hole pair, and
subsequent recombination of the electron-hole pair to emit a
photon. Luminescence which results from a chemical reaction is
usually referred to as "chemiluminescence". Luminescence produced
by a living organism is usually referred to as "bioluminescence".
If photoluminescence is the result of a spin-allowed transition
(e.g., a single-singlet transition, triplet-triplet transition),
the photoluminescence process is usually referred to as
"fluorescence". Typically, fluorescence emissions do not persist
after the exciting cause is removed as a result of short-lived
excited states which may rapidly relax through such spin-allowed
transitions. If photoluminescence is the result of a spin-forbidden
transition (e.g., a triplet-singlet transition), the
photoluminescence process is usually referred to as
"phosphorescence". Typically, phosphorescence emissions persist
long after the exciting cause is removed as a result of long-lived
excited states which may relax only through such spin-forbidden
transitions. A "luminescent label" may have any one of the
above-described properties.
[0083] Suitable chemiluminescent sources include a compound which
becomes electronically excited by a chemical reaction and may then
emit light which serves as the detectible signal or donates energy
to a fluorescent acceptor. A diverse number of families of
compounds have been found to provide chemiluminescence under a
variety or conditions. One family of compounds is
2,3-dihydro-1,4-phthalazinedione. A frequently used compound is
luminol, which is a 5-amino compound. Other members of the family
include the 5-amino-6,7,8-trimethoxy- and the dimethylamino[ca]benz
analog. These compounds can be made to luminesce with alkaline
hydrogen peroxide or calcium hypochlorite and base. Another family
of compounds is the 2,4,5-triphenylimidazoles, with lophine as the
common name for the parent product. Chemiluminescent analogs
include para-dimethylamino and -methoxy substituents.
Chemiluminescence may also be obtained with oxalates, usually
oxalyl active esters, for example, p-nitrophenyl and a peroxide
such as hydrogen peroxide, under basic conditions. Other useful
chemiluminescent compounds that are also known include -N-alkyl
acridinum esters and dioxetanes. Alternatively, luciferins may be
used in conjunction with luciferase or lucigenins to provide
bioluminescence.
[0084] In some embodiments immunoassays are run on the fluidic
device. While competitive binding assays, which are well known in
the art, may be run in some embodiments, in preferred embodiments a
two-step method is used which eliminates the need to mix a
conjugate and a sample before exposing the mixture to an antibody,
which may be desirable when very small volumes of sample and
conjugate are used, as in the fluidic device of the present
invention. A two-step assay has additional advantages over the
competitive binding assays when use with a fluidic device as
described herein. It combines the ease of use and high sensitivity
of a sandwich (competitive binding) immunoassay with the ability to
assay small molecules.
[0085] In an exemplary two-step assay shown in FIG. 10, the sample
containing analyte ("Ag") first flows over a reaction site
containing antibodies ("Ab"). The antibodies bind the analyte
present in the sample. After the sample passes over the surface, a
solution with analyte conjugated to a marker ("labeled Ag") at a
high concentration is passed over the surface. The conjugate
saturates any of the antibodies that have not yet bound the
analyte. Before equilibrium is reached and any displacement of
pre-bound unlabelled analyte occurs, the high-concentration
conjugate solution is washed off. The amount of conjugate bound to
the surface is then measured by the appropriate technique, and the
detected conjugate is inversely proportional to the amount of
analyte present in the sample.
[0086] An exemplary measuring technique for a two-step assay is a
chemiluminescence enzyme immunoassay as shown in FIG. 11. As is
known in the field, the marker can be a commercially available
marker such as dioxitane-phosphate, which is not luminescent but
becomes luminescent after hydrolysis by, for example, alkaline
phosphatase. An enzyme such as alkaline phosphatase is also passed
over the substrate to cause the marker to luminesce. In some
embodiments the substrate solution is supplemented with enhancing
agents such as, without limitation, fluorescein in mixed micelles,
soluble polymers, or PVC which create a much brighter signal than
the luminophore alone. Moreover, an alkaline phosphatase conjugate
with a higher turnover number than that used in the commercial
assay is employed. This allows signal generation to proceed much
more rapidly and a higher overall signal is achieved. The increased
sensitivity of the two-step chemiluminescent enzyme immunoassay
(TOSCA) is illustrated in FIG. 12. FIG. 12 shows that for analytes
in the picomolar concentration, TOSCA is able to provide a more
robust signal (higher sensitivity) than a competitive binding
assay. Use of a two-step binding assay thus contributes to higher
sensitivity capabilities of the present invention.
[0087] In some embodiments, unbound conjugates may need to be
washed from a reaction site to prevent unbound conjugates from
activating the substrate and producing and inaccurate signal. It
may be difficult to remove conjugates sticking to the edges of the
reaction sites in such a fluidic device if, for example, there is
not an excess of a wash solution. To decrease the signal
contributed from unbound conjugates stuck to the edge of a reaction
site, it may be advantageous to expand the reaction site edge or
wall radius in order to distance stuck conjugate from the desired
actual detection area, represented by bound probes. FIGS. 14A and
14B illustrates this concept. Reaction site 6 contains reaction
surface 24 and edge or wall surface 26. An edge surface 26 is shown
at a greater distance from the center of the reaction site 6 than
is the edge surface of the prior art design. This allows unbound
conjugates to adhere to the edge surfaces and be distanced from
bound conjugates, which are concentrated closer to the center of
the reaction site 6.
[0088] In preferred embodiments of the invention the fluidic device
includes at least one waste chamber to trap or capture all liquids
after they have been used in the assay. In preferred embodiments,
there is more than one waste chamber, at least one of which is to
be used with a calibration assembly described herein below.
On-board waste chambers also allow the device to be easily
disposable. The waste chamber is preferably in fluidic
communication with at least one reaction site.
[0089] The subject system is capable of detecting a plurality of
analytes. In one aspect, the system can be used to identify and
quantify analytes present varying concentrations that differ by
more than 3 orders of magnitude.
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