Immobilization of invertase and glucose oxidase in conducting H-type polysiloxane/polypyrrole block copolymers Altan G€ ursel a , Selmiye Alkan b , Levent Toppare b, * , Yusuf Ya gcı c a Department of Polymer Science and Technology, Middle East Technical University, 06531 Ankara, Turkey b Department of Chemistry, Middle East Technical University, 06531 Ankara, Turkey c Department of Chemistry, Istanbul Technical University, 80626 Istanbul, Turkey Received 24 October 2002; received in revised form 3 June 2003; accepted 25 July 2003 Abstract In this study, immobilizations of enzymes, invertase and glucose oxidase, were achieved in conducting copolymers of N-pyrrolyl terminated polydimethylsiloxane/polypyrrole (PDMS/PPy) matrices via electrochemical polymerization. The kinetic parameters, v max (maximum reaction rate) and K m (substrate affinity), of both free and immobilized enzymes were determined. The effect of supporting electrolytes, p-toluene sulfonic acid and sodium dodecyl sulfate, on enzyme activity and film morphologies was examined. The optimum temperatures and operational stabilities of immobilized enzymes were determined. PDMS/PPy copolymer matrix was found to exhibit significantly enhanced properties compare to pristine polypyrrole in terms of relative enzyme activities, kinetic parameters and operational stabilities. Ó 2003 Published by Elsevier B.V. Keywords: Immobilization; Invertase; Glucose oxidase; Polysiloxane; Electropolymerization 1. Introduction Enzymes are the biocatalytically active entities upon which the metabolism of all living organism is based. They facilitate biochemical reactions by lowering the energy of activation [1]. An immobi- lized enzyme is one which has been attached to or enclosed by an insoluble support medium or one where the enzyme molecules have been cross- linked to each other, without loss of catalytic ac- tivity [2]. Immobilized enzymes provide several opera- tional advantages over free enzyme. The reusabil- ity without significant loss of activity, enhanced stability, controlled product formation, ease of separation of enzyme from reaction products and high enzymatic activity in a small volume are the attractive features of immobilized systems. Invertase (EC 3.2.1.26) catalyses the conversion of sucrose to glucose and fructose. This hydrolysis reaction, yielding sugar mixtures, is widely used in the production of noncrystallizing creams, in making jam and artificial honey. Invertase has Reactive & Functional Polymers 57 (2003) 57–65 www.elsevier.com/locate/react REACTIVE & FUNCTIONAL POLYMERS * Corresponding author. Tel.: +90-312-210-32-51; fax: +90- 312-210-12-80. E-mail address: toppare@metu.edu.tr (L. Toppare). 1381-5148/$ - see front matter Ó 2003 Published by Elsevier B.V. doi:10.1016/j.reactfunctpolym.2003.07.004