| Abstract [eng] |
Scanning electrochemical microscopy (SECM) is an innovative method, which could be applied for the surface-activity analysis of enzymatic biosensors and biofuel cells. The SECM is based on electrochemical measurements performed by ultramicroelectrode (UME), which is scanning the 3D space, which is close to surface of the interest that is containing catalytic, redox or other electrochemically active sites. In such experiments the UME is mostly connected as a working electrode in electrochemical setup, and the current, which is measured by the UME, depends on the local concentration of electroactive species. In this work, SECM was applied for the investigation of biosensors’, when biorecognition elements are enzymes and living cells. For this purpose, enzyme Glucose oxidase and yeasts cells Saccharomyces cerevisiae were selected, and different modes of SECM were applied using electrodes of different geometry. It was found, that Generation-Collection and Redox Competition modes of SECM are suitable for the investigation of biosensor’s surface. At the same time the formation of product of enzymatic reaction (H2O2) and consumption of reactant – O2 kinetics’ can be determined and visualized in 3D space. Redox Competition SECM mode could be applied for simplified determination of Michaelis constant, when only approaching curves of SECM are recorded. Determination of diffusion of reaction products from biosensors’ or biofuel cells’ surfaces in real time can be performed by combined SECM and Electrochemical Impedance Spectroscopy system. The surface of biosensors modified by living cells devoted for the determination of toxicity can be investigated by Generation-Collection SECM mode using two redox mediators based system; one of which is lipophilic toxic 9,10-Phenanthrenequinone, and a second – hydrophilic ferricyanide. For the determination of cell viability at different pH the Hill’s function was successfully applied. The calculation of Hill’s number has showed that the 9,10-Phenanthrenequinone has high degree of cooperativity to yeast cells at different pH. |
