Direct electron transfers study of immobilized tyrosinase using the modified glassy carbon electrode by MWCNT/ poly (aniline-co-metha phenylene diamine) composite

In this research, tyrosinase (Tyr) was immobilized on the modified glassy carbon electrode (GCE) by carboxylated multi walled carbon nanotube (MWCNT)/ poly (aniline-co-metha phenylene diamine) (PAN-Pd) and its direct electron transfer rate (DET) was studied using cyclic voltammetry (CV). A pair of well-defined quasi-revesible voltammetric peaks were observed which corresponding to the Cu (II)/ Cu (I) redox couple located in the active site of Tyr. The formal potential of immobilized enzyme was measured to be -42 mV (vs. Ag/AgCl) in phosphate buffer solution at pH 7.0. The apparent heterogeneous electron transfer rate constant and charge-transfer coefficient were estimated to be 2.2 s−1 and 0.5, respectively. The surface coverage of Tyr on the surface of the modified electrode was calculated to be 1.3×10−10 mol/cm2.