Polyaniline-coated microtiter plates for use in longwave optical bioassays

A technique for coating the wells of microtiter-plates with polyaniline lay ers and with polyaniline/enzyme layers is presented. The resulting wells ar e shown to be useful for assaying enzyme substrates (as exemplified for glu cose via pH) and hydrogen peroxide (via the redox properties of the film). Analyte detection is based on monitoring the absorption spectra of the poly aniline, which turn purple as a result of redox processes, or green on form ation of acids by enzymatic reactions. Hydrogen peroxide (a species produce d by all oxidases) and glucose (which yields protons on enzymatic oxidation ) have been determined in the millimolar to micromolar concentration range. High sensitivity, film stability and good reproducibility of the measureme nts make the system an attractive alternative to existing biosensing scheme s.