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New types of polymeric membranes with molecular recognition sites for L-phenylalanine (L-Phe), 6-amino-1-propyluracil (APU), atrazine, and sialic acid have been prepared using the molecular imprinting approach. The membrane synthesis includes radical polymerization of ethylene glycol dimethacrylate (EDMA) and functional monomers in the presence of a template. Several compoundss-(diethylamino)ethyl methacrylate (DEAEM), methacrylic acid (MAA), allylamine (AA), and (4-vinylphenyl)boronic acidswere as functional monomers, which are able to form covalent, ionic, or hydrogen bonds with the corresponding templates. Template specific conductometric sensors, based on these polymers, were constructed and studied. An opposite response of covalently versus noncovalently imprinted membranes was demonstrated and discussed in detail. Sensors based on these materials could detect the target molecules at concentrations of 1-50 µM in solution. The high specificity and stability of these imprinted membranes render them promising alternatives to enzymes, antibodies, and other natural receptors usually used in sensor technology.

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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.

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