Multiwalled Carbon Nanotube-CaCO 3 Nanoparticle Composites for the Construction of a Tyrosinase-Based Amperometric Dopamine Biosensor Magdalena-Rodica Bujduveanu, a Wenjuan Yao, b, c Alan Le Goff , b Karine Gorgy , b Dan Shan, c Guo-Wang Diao, c Eleonora-Mihaela Ungureanu,* a Serge Cosnier* b a University “Politehnica” of Bucharest, Faculty of Applied Chemistry and Material Science, Gh. Polizu 1–7, 011061, Bucharest, Romania b UniversitØ Joseph Fourier, DØpartement de Chimie MolØculaire UMR-5250, ICMG FR-2607, CNRS, Grenoble, France c School of Chemistry & Chemical Engineering, Yangzhou University, Yangzhou 225002, P.R. China *e-mail: em_ungureanu2000@yahoo.com; serge.cosnier@ujf-grenoble.fr Received: May 14, 2012; & Accepted: June 21, 2012 Abstract We report the fabrication of a highly sensitive dopamine biosensor based on the entrapment of tyrosinase into CaCO 3 nanoparticles at Multiwalled Carbon Nanotube (MWCNT) electrodes. CaCO 3 acts as host matrix for tyrosi- nase and MWCNT provides a highly porous conductive network enhancing the enzyme immobilization and the electrochemical transduction of the enzyme reaction by boosting the amplification phenomenon involved in the bio- sensing of catechol and dopamine. The comparison of the performance of CaCO 3 -tyrosinase electrodes with and without MWCNT film clearly indicates the improvement in sensitivity and maximum current brought by the combi- nation of MWCNTs and inorganic nanomaterials. These nanostructured hybrid bioelectrodes exhibit a high sensitiv- ity for the detection of catechol and dopamine, namely 35.7 A mol À1 L cm À2 , the detection limit for dopamine being 15 nmol L À1 with no influence of the presence of interferents, i.e. uric acid and ascorbic acid. Keywords: Biosensors, Carbon nanotubes, Calcium carbonatenanoparticles, Dopamine biosensing, Tyrosinases DOI: 10.1002/elan.201200245 Supporting Information for this article is available on the WWW under http://dx.doi.org/10.1002/elan.201200245. 1 Introduction Dopamine belongs to the catecholamine family and is im- plicated in many nervous system disorders such as Parkin- sons disease. The real-time and localized detection of low dopamine levels into the brain is of particular impor- tance in the study of neuronal signaling. Many efforts have been made to achieve fast-responsive and highly sensitive detection of dopamine. Among the various ana- lytical techniques for dopamine determination, electro- chemical methods received particular attention because of the low equipment costs and the possibility to use ul- tramicroelectrodes. While methods based on the direct electrochemical oxidation of dopamine have the advan- tages to be achievable by many electrocatalytic materials, they suffer from the interfering effects of other oxidizable metabolites and a poor reproducibility due to electrode passivation. An alternative to these methods is the use of biosen- sors. Even if, in many case, stability over time need im- provements, the electrochemical biosensors have been in- creasingly developed for in situ monitoring in environ- mental and health care applications due to their advan- tages in terms of simplicity, portability, short response time and high selectivity [1]. In particular, biosensors based on tyrosinase enzymes (or polyphenol oxidases) constitute a highly selective sensor for phenolic and di- phenolic compounds such as catechol, phenol, or dopa- mine [2]. In contrast to electrochemical methods, the transduction step is based on the reduction of the enzy- matically generated quinone derivatives. Indeed, the use of tyrosinase that catalyzes the oxidation of phenolic compounds, is an efficient means of avoiding interferenc- es with other redox species like ascorbic or uric acids. In the case of tyrosinase-based biosensors, main bottlenecks lie in the efficient immobilization of a high enzyme amount providing electroactive products that can be de- tected at the electrode surface. In addition, the immobili- zation should create a suitable microenvironment for the long-term conservation of enzyme activity. Different im- mobilization strategies were already employed to build selective and sensitive tyrosinase biosensors. For instance, conjugated polymers, clays and ceria-titania/chitosan bio- composites were used to entrap tyrosinase leading to in vivo measurements of low levels of dopamine into the brain of rats [3–5]. To improve the analytical characteristics of this type of biosensor, three-dimensional bioconfigurations must be TOPICAL CLUSTER Electroanalysis 2012, 24, No. &,1–7  2012 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim &1& These are not the final page numbers! ÞÞ Full Paper