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(θ')) 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 (Γ(*)) of the electroactive Mb in the Chit-MWNTs film was estimated to be (4.16±0.35)×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 2.5×10(-5) M to 2.0×10(-4) M with a detection limit of 1.02×10(-6) M (S/N=3). Moreover, the biosensor displays rapid response to H(2)O(2) and good stability and reproducibility.