System and method for precision detection of biomarkers

Abstract

A method for detecting biomarkers with shortened test time and enhanced precision is provided. A sample from the body fluid is made to flow over a sensor surface coated with a capture antibody to allow binding of a biomarker in the sample to the capture body. An optical method detects and counts the individual binding events along the sensor surface with single molecule resolution, and difference in the binding events along the sensor surface is detected in real-time and analyzed to determine the biomarker concentration.

What is claimed is: 
     
         1 . A method for quantitative detection of a biomarker in a fluidic sample flowing through a microfluidic channel and over a sensor surface coated with a first antibody, the method comprising:
 introducing a sample containing a biomarker into the microfluidic channel to flow over the sensor surface;   illuminating the sensor surface;   allowing the biomarker in the sample to bind to the first antibody on the sensor surface;   imaging light scattered by the binding events of the biomarker to the first antibody on the sensor surface; and   employing a processor executing machine readable instructions to perform the following: select at least two zones on the sensor surface, count a number of binding events of the biomarker to the first antibody in the two zones, determine a difference in the numbers of the binding events of the biomarker to the first antibody in the two zones, and determine a concentration of the biomarker from the difference in the numbers of the binding events of the biomarker to the first antibody in the two zones using a calibration curve.   
     
     
         2 . The method of  claim 1 , further comprising adding to the microfluidic channel a second antibody conjugated with nanoparticles to bind to the biomarkers that are bound to the first antibody. 
     
     
         3 . The method of  claim 2 , further comprising:
 filtering to reduce noise and increase signal-to-noise ratio to ensure that single nanoparticles can be imaged;   counting individual nanoparticles in real time; and   comparing a difference or gradient in the numbers of binding events of the biomarker to the first antibody to a concentration of the biomarker.   
     
     
         4 . The method of  claim 3 , further comprising evaluating statistical variability in the numbers of binding events to determine sufficiency of a time of detection. 
     
     
         5 . The method of  claim 2 , wherein the nanoparticles comprise gold nanoparticles. 
     
     
         6 . The method of  claim 1  wherein the biomarker is selected from the group consisting of troponins, proteins, peptides, exosomes, hormones, neurotransmitters, metabolites, and nucleic acids. 
     
     
         7 . A system for detection of an analyte, comprising:
 a sensor having a reflective metal surface and a plurality of capture antibodies, each antibody being tethered by a linker, where each tethered antibody is spaced apart from each other tethered antibody by at least one spacer;   a light source located at an incident angle with respect to the reflective metal surface;   a camera positioned to receive scattered and reflected light from the sensor and configured to produce a plurality of raw plasmonic images;   an image processor coupled to the camera and configured to generate a plurality of processed images by removing background noise from the plurality of raw plasmonic images using differential imaging algorithms executed by a computer, where each processed image of the plurality of processed images is generated from a corresponding unique one raw plasmonic image of the plurality of raw plasmonic images; and   an automated counter coupled to the image processor and configured to perform real-time particle counting on the plurality of processed images to detect number of single gold nanoparticles immobilized by the tethered antibodies of the plurality of tethered antibodies.   
     
     
         8 . The system of  claim 7 , wherein the gold nanoparticles comprise streptavidin coated gold nanoparticles. 
     
     
         9 . The system of  claim 8 , wherein the capture antibodies are configured to bind procalcitonin having a bound detection antibody, and the bound detection antibody is configured to bind the streptavidin coated gold nanoparticles. 
     
     
         10 . The system of  claim 9 , further comprising a delivery device for delivering a sample solution including procalcitonin (PCT) to the sensor. 
     
     
         11 . The system of  claim 7 , wherein the linker comprises a polyethylene glycol (PEG) linker. 
     
     
         12 . The system of  claim 7 , wherein the light source comprises a superluminescence diode and an oil immersion objective.