Application of scanning electrochemical microscopy in bioanalytical chemistry

Abstract

For more than six decades electroanalytical microsensors have been employed in experimental life sciences for investigation of physiological processes. Researchers have been able to assess concentration of different species with good temporal and spatial resolution at the vicinity or inside of biologic objects. In the eighties of the last century a remarkable technique, the so-called probe microscopy, has been developed for studying the microworld. It is named scanning probe microscopy. Scanning tunneling microscopy (STM) and the atomic force microscopy (AFM) were the first probe microscopy methods. Soon after these the electrochemical version of the probe microscopy, the scanning electrochemical microscopy (SECM) appeared, resulted by the pioneering work of Bard and Engstrom. One of the most promising application fields of SECM is the bioanalysis. The availability of sophisticated, easy to use scanning probe instruments and the development of theoretical background boosted the popularity of electrochemical microscopy in biosciences. SECM uses high precision three-dimensional positioning devices, electrochemical microsensor tip and computer controlled measuring, evaluating and image formation algorithm; voltammetric, potentiometric, and conductance measuring methods have been successfully employed for studying biological objects or processes. Accordingly miniaturized voltammetric working electrodes, ion selective potentiometric microsensors, or conductance measuring microprobes have been used as measuring tips. SECM measurements showed details of topographic changes or gas exchange processes over living botanic samples. Metabolic activity of living individual cells or cell colonies could be studied without major invasion. Topographic changes of surface confined cells, transport of different materials through bio-layers could be assessed. Influence of chemical, radiation, or physical effects on the metabolic activity or surviving rate could be studied. The following chapter shortly summarizes the basics of the SECM and briefly introduces a few examples where the method was advantageously used in experiments of life sciences.