Electrosynthesis and permselective characterisation of phenol-based polymers for biosensor applications Original Research Article

A range of mono- and di-substituted phenol monomers were investigated as candidates for the generation of electrosynthesised polymers to act as permselective membranes in Pt-based amperometric biosensors. Two analytes were used as permeability probes: the enzyme signal transduction molecule in first generation biosensors, H2O2; and the archetypal interference species in biological applications, ascorbic acid (AA). A selectivity parameter, S (%), defined as the ratio of AA to H2O2 responses, was used to rank the polymers. Two previously reported electrodes were used as benchmarks: bare Pt and Pt modified with a poly(1,2-diaminobenzene)/albumin composite, Pt/PPD-BSA. The AA-blocking characteristics of poly(phenol) were better than the benchmarks, but low H2O2 permeability gave high (poor) S (%) values. In contrast to the effects of proteins on PPD, incorporation of albumin into the poly(phenol) matrix made the polymer more permeable to AA. Modification of the phenol monomer with alkyl substituents also increased the permeability of the resulting polymers to AA. Analogous modifications with halogens significantly improved the AA-rejecting properties of these polymers, with Pt electrodes modified with polymers generated from 2,6-difluorophenol showing four orders of magnitude lower sensitivity to AA compared with bare metal. Electrochemical QCM measurements indicated that poly(phenol) films electrosynthesised on Pt at pH 7.4 were significantly thinner (3±1 nm) than PPD membranes (20±3 nm).