Evaluation of amperometric microsensors for protein screening tasks

The characterisation and comparison of different sensor materials to find the optimum configuration for amperometric protein screening tasks is presented. The well-known enzyme glucose oxidase (GOD) served as a test vehicle. The study was performed on test chips, which were fabricated in thin film technology using glass and silicon base materials. Each single chip contained a group of eight microsensors each one equipped with its own pseudo-reference electrode (two-electrode configuration). The pseudo-reference electrodes were fabricated in platinum and some of them were covered with an additional thin film layer of Ag/AgCl. The microsensors were characterised by cyclic voltammetry using the [Fe(CN)6]3−/[Fe(CN)6]4− redox couple and calibration curves was obtained with test solutions containing different concentrations of hydrogen peroxide. The oxidation reaction of glucose catalyzed by GOD was used in order to check and quantify the presence of this enzyme in different test samples. It was demonstrated that protein concentrations in the femtomolar range together with small sample volumes of a few μl - adequate for protein screening tasks - could be investigated with amperometric methods. As a result, the sensors with the pseudo-reference electrodes fabricated in platinum turned out to be extremely stable.