Abstract: The matrix for laccase immobilization consisting of chitosan-g-N-carboxymethyl-2-sulfo-4,5-2H-imidazolinone(CTS-g-N-CSIDZ) and multiwall carbon nanotubes(MWCNTs) was prepared through MWCNTs non-covalently functionalized with CTS-g-N-CSIDZ. Laccase immobilization on the composite carrier was achieved mainly by physical adsorption together with active centers in laccase complexing with ligands on the carrier and therefore the immobilized laccase could retain its original conformation of active centre to a great extent. On the glassy carbon electrode modified by the composite with adsorbed laccase was fabricated by a layer of composite composed with entrapped laccase attached to the surface of bare electrode. On the basis of determinoffing the loading of the composite matrix towards laccase, specific activity of immobilized laccase, stability, reusability and catalytic 2,6-dimethoxyphenol(DMP) oxidization dynamic parameters of the immobilized laccase on the composite matrix, function of this chemical sensor based on the electrode modified with the composite which accommodated laccase were examined(DMP as substrate). Results indicated this composite matrix for laccase entrapment had superiority of high enzyme loading amount(81.7 mg/g), improved laccase specific activity in immobilized state(1.33 U/mg). While the entrapped laccase in composite modified electrode as electrochemical sensor showed favorable affinity towards its substrate:DMP(MichaelisMenten constant KM is 0.0918 mmol/L), relatively higher sensitivity to DMP(3.680 mA·L/mol), lower detection limit for DMP(3.3×10-4 mmol/L), its relatively higher responsible selectivity, favorable reproducibility, reusability and excellent long-term stability were obtained. Such advantages make this laccase-based electrode one of promising candidates as amperometric electrochemical sensor for application in sensing the specific phenol-like compound selectively.

Key words: laccase, multiwall carbon nano-tubes, Chitosan, enzymatic dynamics, chemical sensor