Optical resonance coupling between a side-polished fiber and thin film waveguides has been investigated in the presence of biochemical adsorbates. The shift of the resonance wavelengths was found to be highly sensitive to the capture of target DNA recognition elements with Au nanoparticle markers, allowing for a sensitivity limit of 10 particles on the side-polished fiber core area (2000 μm²) during on-line measurements using a polychromator spectrometer.