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

Flow injection methodology was used to electropolymerize pyrrole and o-phen ylenediamine over an electrode substrate consisting of the organic conducti ng salt (OCS) tetrathiafulvalene-p-tetracyanoquinodimethane (TTF-TCNQ), usi ng a cyclic scan of potentials from +100 to +650 mV vs Ag/AgCl down arrow. The enzyme glucose oxidase (GOx) was previously entrapped and cross-linked with glutaraldehyde within the OCS in order to construct a glucose enzyme s ensor. The sensitivity and dynamic features of enzyme biosensors coated wit h 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 s alt efficiently re-oxidizes reduced sites in flavin adenine dinucleotides, thereby allowing the sensor to operate at low potentials. The selectivity a gainst the electroactive interferents ascorbic acid (AA) and uric acid (UA) is substantially improved relative to bare electrodes as a result of the m olecular exclusion properties of PPy and oPPD in both the monolayer and bil ayer coated sensors. The OCS-GOx/PPy monolayer sensor was used for the enzy matic determination of glucose in a synthetic serum sample. The proposed en zyme 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 determination s had been carried out. (C) 1999 Elsevier Science B.V. All rights reserved.