The research interest is guided by the elucidation of electron-transfer mechanisms at interphases. This implies the development of reagentless amperometric biosensors based on novel sensor architectures. All components which are essential for the function of the envisaged sensor are immobilized on the surface of an appropriate electrode allowing their interaction as a basis for the final generation of a concentration-dependent signal. Thus, new strategies for the deposition of conducting-polymer films, the pH-induced precipitation of poly(acrylate)-based non-conducting polymers, and the application of self-assembled monolayers are investigated. The heterogeneous electron transfer between an immobilized biological recognition element (in general an enzyme) and the electrode surface occurs by using the conductivity of the polymer matrix (molecular cable) or by means of redox relays covalently attached to the polymer backbone. The synthesis of electrochemically polymerisable redox polymers, the selective modification of microelectrodes and electrode arrays, as well as the investigation and elucidation of electron-transfer processes in redox polymers is an ai, of the investigations. Besides the synthesis of related compounds, new electroanalytical methods are developed allowing for the description of the electron-transfer processes in redox polymers.
Since 1992 scanning electrochemical microscopy (SECM) was used as a tool for the investigation of sensor surfaces with high lateral resolution. For this, the fabrication of ultramicroelectrodes is indispensable, and recently we succeeded in the reliable fabrication of glass-insulated nanoelectrodes with diameters down to 50 nm. For the accurate positioning of these nanotips a shear-force dependent feedback loop was established which allows for the secure approach of the nanotip to the investigated surface to a distance below 100 nm. Based on these apparative developments different applications of high-resolution SECM were investigated such as the visualization of localized corrosion at NiTi shape-memory alloys, local potentiometric measurements of ions using ionophor-based microsensors, the detection of the secretion of neurotransmitters from single neurons during stimulated exocytosis, the release of NO and glutamate upon stimulation, the local detection of cell metabolism via O2 consumption. New developments are concerned with the parallelization of SECM allowing for the simultaneous positioning of up to eight microelectrodes for the investigation of compound libraries, parallel biochemical assays. In addition, SECM is used to electrochemically detect DNA hybridization as a basis for novel DNA chips.