Direct Electrochemistry and Nitric Oxide Interaction of Heme Proteins Adsorbed on Nanocrystalline Tin Oxide Electrodes

Abstract

Nanocrystalline, nanoporous metal oxide films are a novel substrate for protein immobilization. Such electrodes allow both electrochemical and spectroelectrochemical studies of the protein redox function and, moreover, provide an attractive approach for the development of both optical and electrochemical biosensors. Previous studies have largely focused on the use of nanocrystalline TiO2 electrodes. In this paper, we extend these studies to nanocrystalline SnO2 electrodes. Immobilization of two proteins, cytochrome c (Cyt-c) and hemoglobin (Hb) is observed to proceed with similar protein loadings for both metal oxides. However, the SnO2 electrode is demonstrated to be preferable to the TiO2 electrode for electrochemical studies of these proteins, as the potential window over which the SnO2 film is conducting is shifted to more positive potentials by 500 mV. Cyclic voltammetry and spectroelectrochemistry are employed to demonstrate that this shift allows the observation of reversible oxidation and reduction of both heme proteins on the SnO 2 electrodes without the use of any electron-transfer promoters or mediators. Electron-transfer rate constants of 1 ( 0.03 and 0.53 ( 0.03 s -1 are determined for the Cyt-c/SnO2 and Hb/SnO2 electrodes, respectively. Finally, we demonstrate that the high protein loading and electrical conductivity of Hb/SnO2 films allow the electrochemical sensing of nitric oxide. Electrochemical sensing is demonstrated, with a limit of detection of 1 µM.

A simple biofuel cell cathode with human red blood cells as electrocatalysts for oxygen reduction reaction

“…Thus, the electrochemical investigations have been mainly performed with adding of mediators and promoters or modified and immobilized electrodes, i.e. by the MET types (Kafi and Crossley, 2013;Yin et al, 2005;Revenga-Parra et al, 2005;Topoglidis et al, 2003;Kawahara and Ohno, 1998;Shan et al, 2007;Shi et al, 2007;Zhao et al, 2006;Feng et al, 2006;Zhang and Oyama, 2004;Jia et al, 2004;Sun and Hu, 2004;Gu et al, 2001). On the other hand, we have demonstrated a simplest DET between Hb molecules and bare indium-tin-oxide (ITO) electrodes and found that the protein structure of Hb molecules on the bare ITO electrode surface should be similar to its own native state the same as that in the solution phase (Ayato et al, 2008;Ayato et al, 2007).…”

Selective determination of urea using urease immobilized on ZnO nanowires

“…Moreover, due to the unique properties of nanostructures/nanomaterials in the biosensing area, nanosensors offer some significant advantages owing to their small size and high surface area to volume ratios allowing larger signals, better catalysis and the more rapid movement of analytes through sensors. Recently, nanostructured materials such as zinc oxide (ZnO) [10][11][12][13][14], cerium oxide (CeO 2 ) [15], tin oxide (SnO 2 ) [16], titanium oxide (TiO 2 ) [17], iron oxide (FeO 2 ) [18] and zirconium oxide (ZrO 2 ) nanoparticles [19] have been used for fabrication of transducer surface because of their unique ability to promote faster electron transfer between electrode and active site of desired enzyme. Among these nanomaterials, ZnO nanostructures receive growing attention due to their unique properties including high specific surface area, high catalytic efficiency, strong adsorption ability, high isoelectric point (IEP 9.5), wide band gap (3.37 eV), biocompatibility and high electron communication features.…”

Nanostructured Metal Oxides Based Enzymatic Electrochemical Biosensors

“…The linearity range was obtained as 4-5 mM with detection limit 7.6 and 7.4 μmol/L and biosensor was stable up to 9 months. Attempts have been made to applied sol-gel tin oxide matrix to heme proteins immobilization for rapid detection of H 2 O 2 (Jia et al, 2005a&b;Topoglidis et al, 2003). Solgel derived bioelectrodes showed better analytical performance in respect to other conventional method prepared bioelectrodes, such as faster response, wider detection range, lower detection limit, better affinity, higher enzyme loading, simpler operation and better storage stability for electrochemical detection of hydrogen peroxide due to the introduction of the collagen to form well-distributed porous three-dimensional structure.…”