Metal-enhanced fluorescence of an organic fluorophore using gold particles.

Particulate gold films were deposited on glass substrates by vapor deposition. Rabbit immunoglobulin G (IgG) was immobilized by physiosorption and then Alexa Fluor anti Rabbit IgG was bound to the protein-coated surfaces. Fluorescence was enhanced with increasing the Au thickness and reached saturation at 30 nm when Alexa Fluor555 anti IgG was used. We also examined the effect of silica spacers between the gold film and the labeled protein. The maximum enhancement was dependent on the thickness of silica and reach maximum at 10 nm. The maximum increase in intensity was about 6-fold. We also bound Alexa Fluor-680 anti IgG to the protein-coated surface, and the maximum enhancement was about 10-fold.