Abstract: Composites of multi-wall carbon nano-tubes(MWCNTs) non-covalently functionalized by polymers with different structures were prepared through co-mixing purified MWCNTs and different polymers. These composites were used to entrap laccase(lac) molecules. The enzyme loading amount of carriers, the specific activity and stability of entrapped laccase on these carriers were determined. After coating glassy carbon(GC) electrodes with these composites, the direct electrochemical behavior of these laccase-based electrodes and their catalytic activity toward oxygen reduction reaction in deaerated phosphate buffer solution were investigated with cyclic voltammetry. The velocity constants of electron transfer between entrapped laccase molecules and electrode were also estimated. Experimental results indicate that the electron transfer could be favored when the polymer contains laccase-phlic functional group or groups which can interact with cofactor of laccase and laccases entrapped in composites retaining original conformation as free laccase. Among these laccase-based electrodes, formal potential of direct electron transfer occurred in lac/NIPAM-co-BPCP-MWCNTs/GC(NIPAM-co-BPCP:N-isopropylacrylamide-co-N-allyl-1-benzoyl-3-phenyl-4，5-dihydro-4-formamidopyrazole)(605 mV) is not only relatively closer to formal potential characterized T1 active site in laccase(580 mV) but also displays faster hetero-phase electron transfer velocity(0.726 s-1), higher enzyme loading(103.5 mg/g), improved immobilized laccase specific activity(1.68 U/mg), higher catalytic activity for oxygen reduction reaction(onset potential of oxygen reduction:820 mV, catalytic peak current at 650 mV:85,5 μA), good reusability and favorable long-term durability.

Key words: laccase, multiwall carbon nano-tubes, polymers, vitreous carbon electrode, direct electron transfer