title: Comparisons of platinum, gold, palladium and glassy carbon as electrode materials in the design of biosensors for glutamate.
abstract: Four electrode materials: Pt, Au, Pd and glassy carbon (GC), were studied to investigate their suitability as substrates in the development of two different classes of glutamate biosensor. Glutamate oxidase cross-linked onto poly(o-phenylenediamine) was chosen as the type 1 biosensor (PPD/GluOx), incorporating PPD as the permselective element to detect H(2)O(2) directly on the electrode surface at relatively high applied potentials. GluOx and horseradish peroxidase/redox polymer modified electrodes (Os(2+)PVP/HRP/GluOx) that relied on enzyme-catalysed H(2)O(2) detection at lower applied potentials were used as type 2 biosensors. The voltammetric and amperometric responses to the enzyme signal transduction molecule, H(2)O(2), and the archetypal interference species in biological applications, ascorbic acid, were determined on the bare and PPD/GluOx-modified surfaces. The amperometric responses of these electrodes were stable over several days of continuous recording in phosphate buffered saline (pH 7.4). The sensitivity of the type 1 biosensors to H(2)O(2) and glutamate showed parallel trends with low limits of detection and good linearity at low concentrations: Pt>Au approximately Pd>>GC. Type 2 biosensors out-performed the type 1 design for all electrode substrates, except Pt. However, the presence of the permselective PPD membrane in the type 1 biosensors, not feasible in the type 2 design, suggests that Pt/PPD/GluOx might have the best all-round characteristics for glutamate detection in biological media containing interference species such as ascorbic acid. Other points affecting a final choice of substrate should include factors such as mass production issues.
authors.affiliation: Department of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland. robert.oneill@ucd.ie
authors.forename: Robert D
authors.initials: RD
authors.lastname: O'Neill
authors.forename: Seung-Cheol
authors.initials: SC
authors.lastname: Chang
authors.forename: John P
authors.initials: JP
authors.lastname: Lowry
authors.forename: Calum J
authors.initials: CJ
authors.lastname: McNeil
mesh_terms: D001205:Ascorbic Acid; D015374:Biosensing Techniques / Q000295:instrumentation*; D002244:Carbon; D002396:Catechols; D004566:Electrodes; D018698:Glutamic Acid / Q000032:analysis*; D006046:Gold; D010165:Palladium; D010984:Platinum
chemical_list: D002396:Catechols; C018599:4-methylcatechol; D018698:Glutamic Acid; D010984:Platinum; D010165:Palladium; D002244:Carbon; D006046:Gold; D001205:Ascorbic Acid