Electropolymerization of pyrrole and phenylenediamine over an organic conducting salt based amperometric sensor of increased selectivity for glucose determination Original Research Article

Flow injection methodology was used to electropolymerize pyrrole and o-phenylenediamine over an electrode substrate consisting of the organic conducting salt (OCS) tetrathiafulvalene–p-tetracyanoquinodimethane (TTF–TCNQ), using a cyclic scan of potentials from +100 to +650 mV vs Ag/AgCl↓. The enzyme glucose oxidase (GOx) was previously entrapped and cross-linked with glutaraldehyde within the OCS in order to construct a glucose enzyme sensor. The sensitivity and dynamic features of enzyme biosensors coated with films of polypyrrole (OCS–GOx/PPy) and poly(o-phenylenediamine) (OCS–GOx/oPPD) strongly adhered to the sensor surface, as well as those of a sensor coated with a bilayer film (OCS–GOx/PPy/oPPD) were examined. The TTF–TCNQ salt efficiently re-oxidizes reduced sites in flavin adenine dinucleotides, thereby allowing the sensor to operate at low potentials. The selectivity against the electroactive interferents ascorbic acid (AA) and uric acid (UA) is substantially improved relative to bare electrodes as a result of the molecular exclusion properties of PPy and oPPD in both the monolayer and bilayer coated sensors. The OCS–GOx/PPy monolayer sensor was used for the enzymatic determination of glucose in a synthetic serum sample. The proposed enzyme biosensors are highly stable and reproducible; they retain over 80% of their initial enzymatic activity for 8–12 days, after daily use in a flow injection analysis system, after a total of 350–600 substrate determinations had been carried out.