Evaluation of amperometric microsensors for protein screening tasks S. Pavoni a, * , C. Sundermeier b , J. Perdomo c , H. Hinkers b a Centro de Investigaciones en Microelectro ´ nica (CIME), Instituto Superior Polite ´cnico Jose ´ A. Echeverrı ´a, Antigua Carretera de Vento, km 8 1/2, Boyeros, Ciudad Habana, P.O. Box 8016, Havana 8, Cuba b Institut fu ¨ r Chemo- und Biosensorik (ICB), Mendelstrasse 7, D-48149 Muenster, Germany c Ministerio de Informa ´ tica y Comunicaciones (MIC), Havana, Cuba Received 29 December 2005; received in revised form 29 June 2006; accepted 3 July 2006 Available online 21 July 2006 Abstract 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 addi- tional 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 pres- ence 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 ll – adequate for protein screening tasks – could be investigated with amper- ometric methods. As a result, the sensors with the pseudo-reference electrodes fabricated in platinum turned out to be extremely stable. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Microelectrode arrays; Amperometric sensors; Biochips; Protein screening 1. Introduction The systematic genome-sequencing programs revealed a lot of genes whose functions are still unknown. A possible approach to get insight in their functions is via the identification of the involved proteins. Most of the research work in pro- teomics has been done so far by 2dim electrophore- sis [1,2]. This method is well suited to compare directly the patterns of different protein fractions. As an advantage 2dim electrophoresis allows fast and high resolution separation. But the method is restricted to proteins smaller than 100 kDa [3,4]. Recently, MALDI-MS (matrix-assisted laser desorption/ionisation mass spectroscopy) was iden- tified as another promising tool to screen protein 0263-2241/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.measurement.2006.07.002 * Corresponding author. Tel.: +53 72663047. E-mail address: sonnia.pavoni@electrica.cujae.edu.cu (S. Pa- voni). Measurement 40 (2007) 708–716 www.elsevier.com/locate/measurement