Direct electron transfers improvement of immobilized tyrosinase using the modified MWCNT-Sp on glassy carbon electrode

In this research, tyrosinase (Tyr) was immobilized on the modified multi walled carbon nanotube (MWCNT) by spermine (Sp) on glassy carbon electrode (GCE) 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 -51 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 1.98 s−1 and 0.5, respectively. The surface coverage of Tyr on the surface of the modified electrode was calculated to be 4.32×10−10 mol/cm2.