In this paper we demonstrate that porous silicon (PS) can be used as an immobilization matrix and a transducer for biosensor applications. Thin layers of PS were fabricted showing fine structure in their reflection spectra, characteristic of longitudinal optical cavity modes, or Fabry-Perot interference fringes. The PS surface was modified by covalently bonding streptavidin to a heterobifunctional linker immobilized to the surface using common silane chemistry. The mode spacing and wavelength in the interference spectrum was modified, by displacing buffer and introducing proteins into the PS layer. Protein-protein interactions between immobilized Streptavidin and biotinylated Protein A followed by Protein A and IgG were detected. The surface was regenerated during the course of the experiment showing reversibility of the sensor at the third layer.
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