Amperometric sensors based on tyrosinase-modified screen- printed arrays S. Sapelnikova *, E. Dock, T. Ruzgas, J. Emne ´us Analytical Chemistry Department, Lund University, P.O. Box 124, S-22 100 Lund, Sweden Received 28 January 2003; received in revised form 15 April 2003; accepted 8 May 2003 Abstract This paper describes the design, development and characteristics of a tyrosinase (polyphenol oxidase) modified amperometric screen-printed biosensor array, with the enzyme cross-linked in a redox  /hydrogel namely the PVI 13 - dmeOs polymer. Two types of Au-screen-printed four-channel electrode arrays, differing in design and insulating layer, were compared and investigated. Au-, graphite-coated-Au- and Carbopack C-coated-Au-surfaces, serving as the basis for tyrosinase immobilisation, were investigated and the performances of the different arrays were evaluated and compared in terms of their electrocatalytic characteristics, as well as operational- and storage stability using catechol as model substrate. It was found that the Carbopack C-coated array was the best choice for tyrosinase immobilisation procedure mainly due to a higher mechanical stability of the deposited enzyme layer, combined with good sensitivity and stability for up to 6 months of use. In the batch mode the biosensors responded linearly to catechol up to 30 mM with limits of detection from 0.14 mM. Parameters from cyclic voltammograms indicated that the reversibility of the direct electrochemical reaction for catechol on the three types of electrode surfaces (no tyrosinase modification) was not the limiting factor for the construction and performance of tyrosinase biosensors. # 2003 Elsevier B.V. All rights reserved. Keywords: Screen-printed arrays; Tyrosinase; Amperometric biosensor 1. Introduction Environmental contaminations by toxic and other hazardous compounds have become a public health concern that has led to a vast expansion of the area of environmental analytical chemistry [1]. To develop fast and reliable pollution monitoring instruments, the potential of biosensors has fre- quently been emphasised and there is no doubt that considerable progress has been achieved in the development of biosensors for phenols including chloro- and bromo-phenols, polychlorinated bi- phenols, organophosphoric and carbamate insec- ticides, metal ions, and recently surfactants [2]. The area of biosensors is driven towards devel- opment of small, hand held and battery-operated instruments suited for on-site de-centralized bio- medical- and industrial-analysis, or in the field * Corresponding author. Address: Bashkir State University, 32 Frunze Street, Ufa 450074, Russia. Tel.:  /46-46-222-0104; fax:  /46-46-222-4544. E-mail address: svetlana.sapelnikova@analykem.lu.se (S. Sapelnikova). Talanta 61 (2003) 473  /483 www.elsevier.com/locate/talanta 0039-9140/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0039-9140(03)00314-X