We report on the application of a silica on silicon based planar Bragg grating (PBG) evanescent field sensor as a refractive index biosensor. Our results demonstrate that typical biochemical reactions such as the binding between Biotin (vitamin H) and Streptavidin can be traced in real time on the sensor surface. For the detection of Streptavidin, Biotin was attached to the silanized surface of the planar Bragg grating sensor followed by the immobilization of Streptavidin with a concentration of 7.5nM, 15nM and 30nM, respectively. Real time monitoring capability is highlighted by interrupting the biochemical reaction by applying PBS solution and restarting the reaction several times showing a quasi instantaneous spectral response of the PBG sensor. In addition, applying the same bio-functionalized sensor we have investigated the detection of DNA hybridization. For this purpose, biotinylated single stranded DNA was linked to the sensor surface via Streptavidin. Using this functionalized PBG sensor surface, the DNA hybridization of unlabeled complementary single stranded DNA with a concentration of 5μM can be observed.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.