Polyaniline-coated microtiter plates for use in longwave optical bioassays

A technique for coating the wells of microtiter-plates with polyaniline layers and with polyaniline/enzyme layers is presented. The resulting wells are shown to be useful for assaying enzyme substrates (as exemplified for glucose via pH) and hydrogen peroxide (via the redox properties of the film). Analyte detection is based on monitoring the absorption spectra of the polyaniline, which turn purple as a result of redox processes, or green on formation of acids by enzymatic reactions. Hydrogen peroxide (a species produced 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 measurements make the system an attractive alternative to existing biosensing schemes.