Signal amplification method for surface plasmon resonance-based chemical detection

A method for conducting an assay for a plurality of analytes comprising:

• i) providing a microfluidic channel comprising a surface plasmon resonance active surface;
• ii) immobilizing a plurality of analyte capture agents on the surface in discrete regions to form an array;
• iii) contacting the analyte capture agents with a test solution and a plurality of enzyme labeled reagents specific for the analytes of interest, under conditions for analyte capture agents to form specific complexes with the analytes and the enzyme labeled reagents, wherein the plurality of enzyme labeled reagents are capable of forming a precipitate when reacted with a precipitatable substrate;
• iv) flowing solution having precipitatable substrate of the enzymes through the microfluidic channel so as to contact the complexes with the precipitatable substrate under conditions conducive to formation of the precipitate product for a time period sufficient for precipitate formation;
• and
• v) detecting a change in refractive index near the surface as a function of spatial position on the surface due to precipitate formation, at each discrete region using a SPR signal, wherein the change in the refractive index at a selected location is indicative of amount of the analyte of interest on the surface at the selected location.