Immunocomplexation at wave guiding TiO 2 2 surfaces was investigated using an integrated optical grating coupler. For extended application of this label-free monitoring system, F(ab ) 2 fragments of monoclonal antibodies were photo-immobilized by photolinker polymer-mediated procedures that do not require functionalization of either the immunoreagent or the TiO 2 2 surface. Covalent, light-dependent binding of photolinker polymer and F(ab ) 2 fragments was achieved using a single-step photo-reaction. Bovine serum albumin derivatized with aryldiazirines (T-BSA) served as a photolinker polymer. T-BSA suppressed the non-specific adsorption of analytes to wave guide surfaces. Immunoreagent binding and immunological activity were analyzed and modified surfaces were investigated by scanning force microscopy. Apparent immunoreagent surface densities were 16 7 fmol F(ab ) 2 per mm 2 sensor surface. Optical analyses revealed linear, dose-dependent antigen binding with label free analytes. Immunocompetent surfaces were regenerable by treatment at pH 2 3, rendering the immunosensing system applicable for repetitive use.