Biosensing by optical waveguide spectroscopy based on localized surface plasmon resonance of gold nanoparticles used as a probe or as a label.

The application of localized surface plasmon resonance (LSPR) of gold nanoparticles for the detection of biotin-streptavidin binding, as a typical biological reaction, was investigated by using optical waveguide spectroscopy, and two different modes for the use of gold nanoparticles, one as a probe and the other as a label were compared with each other. The combination with optical waveguide spectroscopy was found to bring about a high sensitivity for the biomolecular detection system using LSPR of gold nanoparticles in both modes. In particular, the mode using gold nanoparticles as a label was demonstrated to be of advantage to devising proper procedures for using nanoparticles and evaluating actual response relevant to the phenomenon concerned, and thus to sensitive detection.