Direct electrochemistry and electrocatalysis of myoglobin-based nanocomposite membrane electrode

The direct electron transfer of myoglobin (Mb) was achieved based on the immobilization of Mb/Silver nanoparticles (AgNPs) on glassy carbon electrode by multi-wall carbon nanotubes (MWNTs)-chitosan( Chit) film. The immobilized Mb displayed a pair of well-defined and reversible redox peaks with a formal potential (E(0)'.) of -24 mV (vs. Ag/AgCl) in 0.1 M pH 7.0 phosphate buffer solution. The apparent heterogeneous electron transfer rate constants (k(s)) of Mb confined to Chit-MWNTs film was evaluated as 5.47 s(-1) according to Laviron's equation. The surface concentration (Gamma*) of the electroactive Mb in the Chit-MWNTs film was estimated to be (4.16 +/- 035) x 10(-9) mol cm(-2). Meanwhile, the catalytic ability of Mb toward the reduction of H(2)O(2) was studied. Its apparent Michaelis-Menten constant for H(2)O(2) was 0.024 mM, showing a good affinity. The linear range for H(2)O(2) determination was from 2.5 x 10(-5) M to 2.0 x 10(-4) M with a detection limit of 1.02 x 10(-6) M (S/N = 3). Moreover, the biosensor displays rapid response to H(2)O(2) and good stability and reproducibility. (C) 2011 Elsevier B.V. All rights reserved.