A biosensor based on photonic crystal surface waves with an independent registration of the liquid refractive index.

A high-precision optical biosensor technique capable of independently determining the refractive index (RI) of liquids is presented. Photonic crystal surface waves were used to detect surface binding events, while an independent registration of the critical angle was used for accurate determination of the liquid RI. This technique was tested using binding of biotin molecules to a streptavidin monolayer at low and high biotin concentrations. The attained baseline noise is 5x10(-13) m/Hz(1/2) for adlayer thickness changes and 9x10(-8) RIU/Hz(1/2) for RI changes.