Optimization of Structural and Optical Parameters of Plasmon Silver Films for IgG-FITC Fluorescent Analysis

The fluorescence enhancement factor of the conjugate of immunoglobulin G labeled with fluorescein isothiocyanate (IgG-FITC) as an immunofluorescent marker was optimized as a function of the optical and topographic parameters of a colloidal silver film on the surface of a standard polystyrene immunoassay plate. The factors influencing fluorescence enhancement were identified. The fluorescence enhancement was shown to be a plasmon-resonance process by using time-resolved spectroscopy, analysis of fluorescence excitation spectra, and enzyme immunoassay determination of the relative concentrations of IgG-FITC adsorbed on the solid phase. The optical density of the silver colloidal film at the excitation and emission wavelengths of IgG-FITC was the most important parameter correlated with the fluorescence enhancement factor. The maximum enhancement factor of 10.2 times was obtained for silver films with the highest optical density.