Mathematical tools for characterization of spatial variability of surface activity based on SECM images

Monika Maciejewska 1Dominik Schäfer 2Wolfgang Schuhmann 2

1. Wrocław University of Technology, Wybrzeże Wyspiańskiego, Wrocław 50-370, Poland
2. Ruhr-Universität Bochum, Anal. Chem. - Elektroanalytik & Sensorik (ELAN), Universitätsstr. 150, Bochum 44780, Germany

Abstract

Scanning Electrochemical Microscopy (SECM) has been successfully used for the imaging of modified surfaces revealing localized chemical information such as immobilized enzyme activity, electron-transfer kinetics etc. [1]. Previously, we have used enzyme microstructures visualized by SECM for compensating for potentially interfering compounds or determination of more than one substrate [2].

It is usually considered that by integration of many differently modified structures the amount of information about a measured sample can be significantly increased as compared to using a single structure. Sensor arrays usually consist of a number of individually and by purpose differently modified sensor surfaces, thus potentially allowing for the evaluation of complex multi-component samples. In contrast, each defined surface area modified with a sensing chemistry exhibits spatial inhomogeneity and could hence be treated similar to a sensor array, provided the possibility to extract localized information.

In order to demonstrate this approach enzyme/polymer layers were fabricated on surfaces and the localized sensor response upon addition of the enzyme's substrate was visualized with high lateral resolution using SECM, in the generator/collector mode (Fig. 1).

abstr1.png

Fig. 1 SECM image of the localized sensor response [nA] of an enzyme/polymer
microspot in the presence of enzyme's substrate.

The SECM images obtained at different substrate concentrations were used as a basis for investigation of spatial variability of surface activity with feature extraction techniques.

[1] Ch. Zhao, G. Wittstock, Biosens. Bioelelectron., 20 (2005) 1277.
[2] S. Gaspar, M. Mosbach, L. Wallman, T. Laurell, E. Csöregi, W. Schuhmann, Anal. Chem., 73 (2001) 4254.

 

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Presentation: Short communication at SMCBS'2005 Workshop, by Monika Maciejewska
See On-line Journal of SMCBS'2005 Workshop

Submitted: 2005-08-31 16:52
Revised:   2009-06-07 00:44