Zwitterionic polymer-modified silicon microring resonators for label-free biosensing in undiluted human plasma

A widely acknowledged goal in personalized medicine is to radically reduce the costs of highly parallelized, small fluid volume, point-of-care and home-based diagnostics. Recently, there has been a surge of interest in using complementary metal-oxide-semiconductor (CMOS)-compatible silicon photonic circuits for biosensing, with the promise of producing chip-scale integrated devices containing thousands of orthogonal sensors, at minimal cost on a per-chip basis. A central challenge in biosensor translation is to engineer devices that are both sensitive and specific to a target analyte within unprocessed biological fluids. Despite advances in the sensitivity of silicon photonic biosensors, poor biological specificity at the sensor surface remains a significant factor limiting assay performance in complex media (i.e. whole blood, plasma, serum) due to the non-specific adsorption of proteins and other biomolecules. Here, we chemically modify the surface of silicon microring resonator biosensors for the label-free detection of an analyte in undiluted human plasma. This work highlights the first application of a non-fouling zwitterionic surface coating to enable silicon photonic-based label-free detection of a protein analyte at clinically relevant sensitivities in undiluted human plasma.