title: Electrochemistry and current control in surface films based on silica-azure redox nanoparticles, carbon nanotubes, enzymes, and polyelectrolytes.
abstract: The redox active nanoparticles were developed by covalently attaching redox dye Azure C (AZU) to commercial silica nanoparticles (SN) via the silylated amine and glutaric dialdehyde links. The SN-AZU nanoparticles were studied as redox mediators for the oxidation of reduced β-nicotinamide adenine dinucleotide (NADH) in two polymeric films. The first film (F1) was composed of SN-AZU, carbon nanotubes, and cationic polyelectrolyte chitosan. The second film (F2) contained also added enzyme glucose dehydrogenase and its cofactor β-nicotinamide adenine dinucleotide (NAD(+)). The films F1 and F2 were cast on the glassy carbon electrodes, covered with an anionic polyelectrolyte Nafion, and their electrochemical properties were probed with NADH and glucose, respectively, using voltammetry, amperometry, and potentiometry. The Nafion overcoat reduced the sensitivity of F1/Nafion film electrodes to NADH by >98%. In contrast, depending on the concentration of Nafion, the sensitivity of the F2/Nafion film electrodes (reagentless biosensors) to glucose increased by up to 340%. The amplification of glucose signal was ascribed to the Donnan exclusion and ensuing Nafion-gated ionic fluxes, which enhanced enzyme activity in films F2. The proposed model predicts that such signal amplification should be also feasible in the case of other enzyme-based biosensors.
authors.affiliation: Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249-0698, USA.
authors.forename: Sushma
authors.initials: S
authors.lastname: Karra
authors.forename: Maogen
authors.initials: M
authors.lastname: Zhang
authors.forename: Waldemar
authors.initials: W
authors.lastname: Gorski
mesh_terms: D001399:Azure Stains / Q000737:chemistry*; D055664:Electrochemical Techniques; D004573:Electrolytes / Q000737:chemistry; D042843:Glucose 1-Dehydrogenase / Q000737:chemistry* / Q000378:metabolism; D015394:Molecular Structure; D053758:Nanoparticles / Q000737:chemistry*; D037742:Nanotubes, Carbon / Q000737:chemistry*; D010084:Oxidation-Reduction; D011108:Polymers / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D001399:Azure Stains; D004573:Electrolytes; D037742:Nanotubes, Carbon; D011108:Polymers; D012822:Silicon Dioxide; D042843:Glucose 1-Dehydrogenase; C045363:Azure C