title: Electron-transfer studies with a new flavin adenine dinucleotide dependent glucose dehydrogenase and osmium polymers of different redox potentials.
abstract: A new extracellular flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenase from Glomerella cingulata (GcGDH) was electrochemically studied as a recognition element in glucose biosensors. The redox enzyme was recombinantly produced in Pichia pastoris and homogeneously purified, and its glucose-oxidizing properties on spectrographic graphite electrodes were investigated. Six different Os polymers, the redox potentials of which ranged in a broad potential window between +15 and +489 mV versus the normal hydrogen electrode (NHE), were used to immobilize and "wire" GcGDH to the spectrographic graphite electrode's surface. The GcGDH/Os polymer modified electrodes were evaluated by chronoamperometry using flow injection analysis. The current response was investigated using a stepwisely increased applied potential. It was observed that the ratio of GcGDH/Os polymer and the overall loading of the enzyme electrode significantly affect the performance of the enzyme electrode for glucose oxidation. The best-suited Os polymer [Os(4,4'-dimethyl-2,2'-bipyridine)(2)(PVI)Cl](+) had a potential of +309 mV versus NHE, and the optimum GcGDH/Os polymer ratio was 1:2 yielding a maximum current density of 493 μA·cm(-2) at a 30 mM glucose concentration.
authors.affiliation: Department of Analytical Chemistry, Lund University, P.O. Box 124, SE-221 00, Lund, Sweden. znadeempk@yahoo.com
authors.forename: Muhammad Nadeem
authors.initials: MN
authors.lastname: Zafar
authors.forename: Xiaoju
authors.initials: X
authors.lastname: Wang
authors.forename: Christoph
authors.initials: C
authors.lastname: Sygmund
authors.forename: Roland
authors.initials: R
authors.lastname: Ludwig
authors.forename: Dónal
authors.initials: D
authors.lastname: Leech
authors.forename: Lo
authors.initials: L
authors.lastname: Gorton
mesh_terms: D004583:Electrons; D005182:Flavin-Adenine Dinucleotide / Q000737:chemistry*; D042843:Glucose 1-Dehydrogenase / Q000737:chemistry*; D009992:Osmium / Q000737:chemistry*; D010084:Oxidation-Reduction; D011108:Polymers / Q000737:chemistry*
chemical_list: D011108:Polymers; D005182:Flavin-Adenine Dinucleotide; D009992:Osmium; D042843:Glucose 1-Dehydrogenase