Scanning electrochemical microscopy (SECM) has become an indispensable tool for the characterization of reactivities at interfaces such as reactions of immobilized enzymes and other biomolecules [1]. The analysis is based on the detection of redox active species generated by an immobilized enzyme though conversion at the scanning ultramicroelectrode (UME).
In addition to localized analysis SECM instruments can be used as tools for microstructuring [2]. By switching between microstructuring and reactivity imaging the success of individual preparation steps can be analysed forming the basis for the rational optimization of such processes.
By patterning self-assembled monolayers (SAM) of alkanethiolates on gold, a surface template can be formed into which enzymatically active layers can be immobilized. Patterned SAMs have been prepared by microcontact printing [3] and localized electrochemical desorption using SECM. By combination of both approaches patterns become available that contain two or more enzymes. Reaction chains and cofactor recycling between different active regions can be studied as a function of the pattern layout at such specimens [4].
Experiments with higher resolution were enabled by production of smaller electrodes and the usage of topographic information of an tunneling microscopic experiment (ECSTM) for positioning the UME in the SECM experiment [5]. Quantitative evaluation of image data is enabled by the use of the boundary element method for simulating coupled transport processes and heterogeneous reactions in systems of arbitrary geometry [6].
1. G. Wittstock, Fresenius J. Anal. Chem. (2001), 370, 303.
2. T. Wilhelm, G. Wittstock; Electrochim. Acta (2001), 47, 275.
3. T. Wilhelm, G. Wittstock, Langmuir (2002), 18, 9486.
4. T. Wilhelm, G. Wittstock, Angew. Chem. Int. Ed. Engl. (2003), 42, 2247.
5. T. Treutler, G. Wittstock, Electrochim. Acta (2003), 48, 2932.
6. O. Sklyar, G. Wittstock, J. Phys. Chem. B (2002), 106, 7499.
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