A novel optical biosensor matrix has been developed to exploit the native fluorescence of certain proteins. This matrix uses a gold colloid monolayer attached to an end of a fiber as a substrate for protein attachment. The effect of the gold monolayer size has been investigated through the techniques of fluorescence, scanning electron microscopy, and transmission electron microscopy. It has been shown that the size of the gold colloid does produce a marked difference in the fluorescence intensity measured. It is surmised through the use of microscopy techniques that the intensity changes seen in the fluorescence emission are not a result of surface coverage, or availability of sites for protein adsorption, but instead of quenching or enhancement by the gold itself.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.