Direct electron transfer reaction of laccase on a glassy carbon electrode modified with 1-aminopyrene functionalized reduced graphene oxide

A biosensor was developed based on the covalent immobilization of laccase (Lac) on 1-aminopyrene (1-AP)-functionalized reduced graphene oxide (rGO)-modified glassy carbon electrode (GCE) by encapsulation with chitosan. X-ray photoelectron spectroscopy and cyclic voltammetry were used to optimize the mass ratio between 1-AP and rGO (rAP/rGO) to be 1/8. Direct electron transfer behavior of Lac immobilized on 1-AP-functionalized rGO (AP-rGO) was investigated by cyclic voltammogram. Results indicate that the AP-rGO is a friendly platform for the immobilization of enzyme, which facilitates the electron exchange between Lac and the modified electrode surface. On AP-rGO/GCE, Lac displayed rapid electron transfer with one participating proton. Furthermore, it was also confirmed that Lac immobilized on the modified electrode exhibited the electrocatalytic response to an established unspecific Lac substrate, 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonate)diammonium salt (ABTS). Without the aid of an electron mediator between Lac and modified electrode, the enzyme-based biosensor shows good reproducibility and high sensitivity to ABTS with a detection limit of 0.1 mu M (S/N = 3). Within the concentration of 2-1000 mu M, a linear relationship was achieved between the current intensity of the electro-catalytic oxidation of ABTS and the concentration of ABTS. The proposed biosensor achieved 95% of steady-state reduction currents within 5 s.