Fiber optic probe with antifouling polymer brush biointerface for bi-modal biosensing in complex liquid samples

We report on the utilization of an antifouling brush biointerface at the surface of surface plasmon resonance (SPR) optical probe for real-world biosensor applications. This biointerface architecture provides the advantage of resistance to fouling when contacted with complex biological fluids, it can be postmodified with functional biomolecular species for affinity biosensor applications, and allows for combined optical and electronic-based biosensing. The SPR optical probe carrying the thin gold film and antifouling polymer brush architecture is successfully implemented as a gate electrode in electrolyte-gated field effect transistor (EG-FET) readout and as a working electrode in cyclic voltammetry (CV). The poly(carboxybetaine acrylamide) (pCBAA) brush was synthesized by the 'grafting from' approach with a thickness matching the evanescent field of surface plasmons. When contacted with water, the film partially swells yielding a thickness of about 100 nm and resistance to fouling from undiluted blood plasma as documented by SPR measurements. In addition, its open structure enables shuttling of charge through the polymer coating and it offers means to investigate this biointerface with combined SPR and FET/CV methods. Such a platform is attractive for the investigation of complex processes on affinity biosensors and provide important leads in design of rapid direct readout of sensitive bioassays with both optical and electronic means.