title: Novel hexacyanoferrate (III)-modified carbon electrodes: application in miniaturized biosensors with potential for in vivo glucose sensing.
abstract: We adapted a new technology for the modification of carbon base electrodes for use as probe-type, potentially implantable glucose sensors. Carbon rods (diameter 0.3 mm) were modified by repeated potential cycling in 0.1 M potassium hexacyanoferrate (III). The modified-carbon electrodes were sealed in plastic pipette tips with an exposed reaction area where glucose oxidase was immobilized using glutaraldehyde. An outer membrane of Nafion, followed by 15% (w/v) polyurethane, was applied over the enzyme layer. The miniature modified-carbon glucose sensors displayed a sensitivity to glucose in phosphate-buffered saline of 91.4 +/- 19 nA/mM (mean +/- SEM) and a linear range up to 5.3 +/- 1 mM glucose when operated at 750 mV versus a silver/silver chloride reference. Corresponding, unmodified-carbon based glucose sensors displayed a lower sensitivity of 20.7 +/- 3 nA/mM with a linear range up to 3.8 +/- 0.5 mM. The modified-carbon glucose sensors responded to glucose when operated in plasma but with a reduced sensitivity compared with that in buffered saline. Glucose sensors displayed good stability for up to 6.5 days during continuous operation in 5 mM buffered glucose solution. Interference from ascorbate and 4-acetamidophenol at both physiological and pharmacological ranges was significantly lower at the modified-carbon base electrodes than that at the unmodified-carbon base electrodes. Also, the relatively large effect of ascorbate and 4-acetamidophenol at the unmodified-carbon base electrode was reduced considerably when the base electrode was coated with glucose oxidase, Nafion and polyurethane membranes.
authors.affiliation: Division of Chemical Pathology, United Medical and Dental Schools, Guy's Hospital, London, UK.
authors.forename: S A
authors.initials: SA
authors.lastname: Jaffari
authors.forename: J C
authors.initials: JC
authors.lastname: Pickup
mesh_terms: D000082:Acetaminophen / Q000737:chemistry; D001205:Ascorbic Acid / Q000737:chemistry; D001234:Aspergillus niger / Q000201:enzymology; D015374:Biosensing Techniques; D004566:Electrodes; D005292:Ferricyanides / Q000737:chemistry; D005947:Glucose / Q000032:analysis*; D005949:Glucose Oxidase / Q000737:chemistry; D008832:Microchemistry
chemical_list: D005292:Ferricyanides; C007931:hexacyanoferrate III; D000082:Acetaminophen; D005949:Glucose Oxidase; D005947:Glucose; D001205:Ascorbic Acid