Preparation and Electrochemical Characterization of an Enzyme Electrode Based on Catalase Immobilized onto a Multiwall Carbon Nanotube-Thionine Film

The present study was aimed at investigating the use of a mixture multiwall carbon nanotube (MWCNT) and thionine (Th) dye in designing of a thionine-based electrochemical biosensor containing catalase (Ct) enzyme (MWCNT-Nafion-Th/Ct) onto a glassy carbon electrode (GCE). The effects of pH, MWCNT concentration and thionine concentration on electrochemical response were explored for optimum analytical performance. The modified electrode exhibited a pair of well-defined, quasi-reversible peaks at formal potential (E degrees') = -0.218 +/- 0.017 V vs. Ag/AgCl corresponding to the Th-ox/Th-red redox couples in the presence of MWCNT, Nafion, and Ct. The electrochemical parameters, including charge-transfer coefficient (0.36), and apparent heterogeneous electron transfer rate constant (4.28 +/- 0.26 s(-1)) were determined. Using differential pulse voltammetry, the prepared enzyme electrode exhibited a linear response to hydrogen peroxide (H2O2) in the range of 10.0-100.0 mu M with a detection limit 8.7 mu M and a sensitivity of 6051.0 mu A mM(-1) cm(-2).