Device and method for detection and quantification of immunological proteins, pathogenic and microbial agents and cells

1. A microfluidic immunoassay device for detecting and measuring an analyte in a liquid sample, comprising a liquid sample inlet defined by an opening for accepting the liquid sample, said liquid sample inlet in continuous fluid connection with a flow resistor channel, said flow resistor channel in continuous fluid connection with an assay inlet of a reaction chamber, wherein the reaction chamber has adsorbed on its surface a plurality of immobilized antigen-specific antibodies (Ab1) specific to an analyte, wherein the surface of the reaction chamber also has a plurality of magnetic-responsive micro-beads desiccated thereon, each of said plurality of magnetic-responsive micro-beads coated with an antigen-specific antibody (Ab2) specific to the analyte, wherein the plurality of antibody-coated magnetic-responsive micro-beads rehydrate, disperse and bind to any analyte present in the liquid sample when the liquid sample flows through the reaction chamber, wherein any analyte present in the liquid sample also binds to the antigen-specific antibodies immobilized on the surface of the reaction chamber to form Ab1-analyte-Ab2-coated magnetic-responsive micro-bead complexes, and wherein any unbound antibody-coated magnetic-responsive micro-beads exit the reaction chamber through an assay outlet, said assay outlet in continuous fluid connection with a micro-channel splitter which bifurcates to form a calibration micro-channel (Co) and at least one test micro-channel (Cm), said at least one test micro-channel and said calibration micro-channel kept at an equal and constant pressure, said calibration micro-channel in continuous fluid connection with a calibration graduated column, and said at least one test micro-channel in continuous fluid connection with at least one test graduated column, wherein one or more magnets creates a magnetic field gradient, said at least one test micro-channel exposed to the magnetic field gradient which causes flocculation of the magnetic-responsive micro-beads in the at least one test micro-channel which reduces flow rate (Qm) of the liquid sample in the at least one test micro-channel compared to the flow rate (Qo) of the liquid sample in the calibration micro-channel, wherein each of the graduated columns has a graduated scale thereon which provides a read-out of the total sample volume flowing through the test micro-channel, Vm, and the sample volume flowing through the calibration micro-channel, Vo, and collected in each of the graduated columns, which read-out is proportional to the concentration, ρ, of Ab1-analyte-Ab2-coated magnetic-responsive micro-bead complexes, which is a function of the concentration of the analyte in the liquid sample.

2. The microfluidic immunoassay device of claim 1 , wherein the ratio Qm/Qo, the difference Qo−Qm, and the ratio (Qo−Qm) p /(Qm) q are calculated, said ratios a proxy for the number of magnetic-responsive micro-beads in the liquid sample, which is a proxy for the concentration of analyte in the liquid sample.

3. The microfluidic immunoassay device of claim 1 , wherein the magnetic field gradient is generated by two magnets aligned lengthwise with the at least one test micro-channel and along opposite poles to expose the at least one test micro-channel to the magnetic field gradient, said at least one test micro-channel located between a gap formed between the opposite poles of the magnets.

4. The microfluidic immunoassay device of claim 1 , wherein the magnetic field gradient is created by one magnet and a magnetic-responsive structure positioned near the at least one test micro-channel.

5. The microfluidic immunoassay device of claim 1 , wherein the magnetic field generated is between about 0.05 Tesla (T) to about 0.5 T, and wherein the magnetic field gradient generated is about 10 T/m or greater.

6. The microfluidic immunoassay device of claim 1 , wherein the total sample volume collected in the calibration micro-channel graduated column serves as a control for parameters such as variation in viscosity between samples, level of hematocrit in blood samples, temperature and humidity fluctuations and sample volumes.

7. The microfluidic immunoassay device of claim 1 , wherein each of the graduated columns has a length of about 20 mm to about 200 mm, a width of about 0.2 mm to about 3.0 mm, and a depth of about 0.1 mm to about 1.0 mm, wherein the respective graduated scales thereon each have a length and a cross-section that is visible to the naked eye, and wherein the read-out, providing a measurement of the unbound magnetic-responsive micro-beads and hence of the concentration of analyte present in the liquid sample, can be obtained at any time by direct comparison of the total sample volume visualized in the calibration graduated column with the at least one test graduated column.

8. The microfluidic immunoassay device of claim 1 , wherein the liquid sample is selected from the group consisting of water, plasma, serum, buffer solution, urine, whole blood, blood analogs, liquid solutions from dilution of solid biological matter, and other biological fluids.

9. The microfluidic immunoassay device of claim 1 , wherein the analyte is selected from the group consisting of proteins, protein fragments, antigens, antibodies, antibody fragments, peptides, RNA, RNA fragments, functionalized magnetic micro-beads specific to CD 4+ , CD 8+ cells, malaria-infected red blood cells, cancer cells, cancer biomarkers such as prostate specific antigen and other cancer biomarkers, viruses, bacteria such as E. coli , and other pathogenic agents.

10. The microfluidic immunoassay device of claim 1 , wherein the device is a single use, portable, lab-on-card device.

11. The microfluidic immunoassay device of claim 1 , wherein the device is fabricated by methods selected from the group consisting of etching each of the micro-channels on a poly(ethylene terephthalate)glycol plastic substrate, using a laser etcher system and then sealing the top of each of the micro-channels in a poly(lactic-co-glycolic acid) plastic by thermal bonding, and by injection mold casting in a poly(methyl methacrylate) plastic.

12. The microfluidic immunoassay device of claim 1 , wherein the concentration of magnetic-responsive micro-beads which can be detected and quantified is about 50 micro-beads/μl to about 2×10 6 micro-beads/μl, and wherein the diameter of the magnetic-responsive micro-beads is about 0.2 μm to about 20 μm.

13. The microfluidic immunoassay device of claim 1 , wherein the at least one test micro-channel and the calibration micro-channel are made of a capillary tube having a length of about 0.2 cm to about 20 cm.

14. The microfluidic immunoassay device of claim 13 , wherein bifurcation of the micro-channel splitter forms one, three or four test micro-channels, and one calibration micro-channel.

15. The microfluidic immunoassay device of claim 14 , wherein bifurcation of the micro-channel splitter forms one test micro-channel and one calibration micro-channel, and wherein the one test micro-channel and the one calibration micro-channel have the same inner diameter of about 50 μm to about 500 μm.

16. The microfluidic immunoassay device of claim 14 , wherein bifurcation of the micro-channel splitter forms three test micro-channels and one calibration micro-channel, wherein each of the three test micro-channels is in continuous fluid connection with one graduated column, wherein the three test micro-channels each have a different inner diameter, wherein the one calibration micro-channel has an inner diameter such that the area of the cross-section of the one calibration micro-channel is identical to the sum of the areas of the cross-sections of the three test micro-channels, and wherein the first test micro-channel has an inner diameter of about 50 μm to about 500 μm, the second test micro-channel has an inner diameter of about 100 μm to about 250 μm, and the third test micro-channel has an inner diameter of about 250 μm to about 5 mm.

17. The microfluidic immunoassay device of claim 14 , wherein bifurcation of the micro-channel splitter forms four test micro-channels and one calibration micro-channel, wherein the four test micro-channels merge to be in continuous fluid connection with one graduated column, wherein the four test micro-channels have the same inner diameter of about 12.5 μm to about 125 μm, and wherein the one calibration micro-channel has an inner diameter such that the areas of the cross-section of the one calibration micro-channel is identical to the sum of the areas of the cross-sections of the four test micro-channels.