Enzyme-metal Oxide Nanoconjugates as Catalysts for Fuel Cells and Biosensors

A new type of conjugate bio-electrocatalyst has been developed using an enzyme (laccase) and metal oxide (TiO2) nanoparticles through a novel multi-step immobilization method. A screen-printed (SP) carbon electrode modified with silylated TiO2 nanoparticles was used for immobilizing the enzyme using as molecular crosslinkers. Scanning electron microscopy images showed no aggregation of nanoparticles during the immobilization process. Cyclic voltammetry characterization of the laccase-TiO2 nanoconjugates as bio-electrocatalysts for O2 reduction reaction revealed that the nanoconjugates displayed excellent activity via mediated electron transfer and significant activity via direct electron transport. The results demonstrate that metal oxides could reliably be used as enzyme supports for bio-electrocatalytic applications. The results reported here have significant implication in the field of biosensors and enzymatic fuel cells Technology Description: The reduction of oxygen to water is one of the most important electrochemical reactions known. Laccase is a metallo-enzyme that catalyzes this reaction particularly well and it has recently shown potential as an electrocatalyst for enzymatic fuel cell cathodes due to its high thermodynamic potential and excellent catalytic properties. Two current issues in enzyme bio-electrocatalysis are the insufficient electrical communication between the enzyme redox site and the electrode and the low active site loading on the electrode due to the large size of enzymes compared to metallic catalysts. These issues can be overcome by providing a large surface area for enzyme immobilization using nanomaterials as enzyme support. A methodology that reliably links the enzyme redox center to low cost semi-conductive metal oxide will therefore significantly benefit enzyme-based bio-electrocatalysis applications. Applications: 1) This invention has significant implications for electrochemical biosensors and enzymatic fuel cells where laccase based catalysts are used for reduction reactions on the cathode. 2) The invention’s application can also be extended to other types of enzymes and metal oxides for applications in enzymatic fuel cells and amperometric biosensors. 3) The results demonstrate that metal oxides could reliably be used as enzyme supports for bio-electrocatalytic applications with significant implications in the field of biosensors and enzymatic fuel cells.