A novel amperometric glucose biosensor based on poly(glycidyl methacrylate-co-(3-thienylmethylmethacrylate)) Osman Karagollu a , Mesut Gorur b , Ali Turkan c , Busra Sengez b, c , Fethiye Gode a , Faruk Yilmaz c, * a Department of Chemistry, Faculty of Arts and Science, Suleyman Demirel University, 32260 Isparta, Turkey b Department of Chemistry, Faculty of Sciences, Istanbul Medeniyet University, 34720 Kadikoy, Istanbul, Turkey c Department of Chemistry, Gebze Institute of Technology, 41400 Gebze, Kocaeli, Turkey article info Article history: Received 8 October 2012 Received in revised form 23 November 2012 Accepted 26 November 2012 Available online 1 December 2012 Keywords: Amperometric biosensor Glucose oxidase Enzyme-modified electrode Covalent immobilization abstract Two novel glucose oxidase (GOx) enzyme electrodes based on the copolymer of glycidyl methacrylate with 3-thienylmethyl methacrylate (poly(GMA-co-MTM)) with and without polypyrrole (PPyr) coating were prepared and employed in the amperometric determination of glucose levels. The effect of PPyr coating on the electrode properties was investigated in detail. Cyclic voltammetry studies showed that electrical conductivity of electrode B with PPyr coating (poly(GMA-co-MTM)/GOx/PPyr) was substantially higher than that of electrode A (poly(GMA-co-MTM)/GOx). On the other hand, electrode A showed better results in terms of sensitivity (10 nA/mM), limit of detection (50.2 mM), and response time (5 s). Electrodes A and B gave linear responses to the glucose concentrations in the range of 2e20 and 2e14 mM, respectively. The ranges of linearity for both enzyme electrodes are sufficient for the determination of physiological glucose concentrations in human blood. Moreover, PPyr coating of electrode B did not result in further stabilization of the enzyme electrode. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction In today’s world, the eating habit of the modern people is changing and more and more processed food is taking part in our daily diet as the time passes. But, the price to be paid is an insidious health problem, impaired glucose tolerance and diabetes mellitus [1]. Diabetes mellitus is one of the most common costly diseases in the contemporary world. Diabetes mellitus is among the provocative factors of retinopathy [2], nephropathy [3], heart disease [4], foot ulcers [5], and lower extremity amputations [6]. Determination of glucose level in blood is a key factor for the early diagnosis and the management of diabetes mellitus [7]. Therefore, significant amount of scientific effort has been directed to the fabrication of selective and sensitive glucose biosensors with short response time [8,9]. Having low cost and long life time are the other desired qualities of the biosensors. The working principle of glucose biosensors relies on the electrochemical oxidation of the analyte (glucose) [10,11]. Enzymatic [10,12] and non-enzymatic [13,14] catalysts for glucose sensing applications were reported in the literature. Enzyme-based biosensors have advantages over non-enzymatic ones; such as the ease of operation, low cost of fabrication, high selectivity and suffi- cient stability for real-time measurements [7]. Since the first enzyme-based glucose biosensor was reported by Clark and Lyons [15], numerous studies devoted to the development of biosensor properties have been conducted. The crucial step for the construction of enzyme biosensors is immobilization of enzymes in the electrode matrices. Entrapment in a carbon paste electrode [16], adsorption on activated surfaces [17], entrapment in a hydrogel [18,19], entrapment in an electropolymerized film [20,21], and covalent bonding [22,23] are common strategies for enzyme immobilization. Enzyme leakage is one of the main problems which affect stabilities of enzyme electrodes [24]. This problem can be surmounted by covalent attachment of enzymes on supporting materials containing proper binding sites [25]. For example, chito- san, a natural polymer with amine functional groups, was used for covalent immobilization of different enzymes [26]. Besides, a variety of synthetic polymers with carboxylic acid [27,28], amino [23], and epoxy [22] functional groups has been developed as immobilization matrices for covalent attachment. Glycidyl methacrylate (GMA) monomer has been used in a variety of polymeric matrices in biosensors to bind enzymes covalently through its epoxy groups [29e31]. Tailor-made designs of these polymers provide opportu- nities to prepare innumerable kinds of materials with desired shapes and functionalities. * Corresponding author. Tel.: þ90 262 605 31 33; fax: þ90 262 605 31 05. E-mail address: fyilmaz@gyte.edu.tr (F. Yilmaz). Contents lists available at SciVerse ScienceDirect Current Applied Physics journal homepage: www.elsevier.com/locate/cap 1567-1739/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cap.2012.11.013 Current Applied Physics 13 (2013) 725e730