Surface plasmon resonance biosensor with anti-crossing modulation readout

A novel approach to surface plasmon resonance (SPR) biosensors providing simplified label-free monitoring of biomolecular affinity binding events is reported. It is based on the interrogation of anti-crossing surface plasmon modes traveling along opposite interfaces of a thin metal film on the top of a tailored multi-periodic grating structure. It allows for diffraction-based backside excitation of surface plasmons without the need of optical matching of the sensor chip to a prism and it allows avoiding of optical probing through the analyzed liquid sample. In conjunction with low angular dispersion of resonantly excited surface plasmon modes, it provides sensitive and versatile optical interrogation of SPR changes associated with biomolecular binding-induced refractive index variations. Direct readout with a fiber optic probe, as well as multi-channel configuration compatible with regular SPR readers, is implemented with the use of sensor chips prepared by mass production-compatible UV-nanoimprint lithography. The potential of the reported SPR sensor chips is illustrated by its ability to characterize affinity interaction of antibodies specific to cancer biomarker CSPG4 on antifouling mixed thiolated self-assembled monolayer with zwitterionic carboxybetaine and sulfobetaine headgroups.