The Investigation of Electrochemistry Behaviors of Tyrosinase Based on Directly-Electrodeposited Grapheneon Choline-Gold Nanoparticles

A novel catechol (CA) biosensor was developed by embedding tyrosinase (Tyr) onto in situ electrochemical reduction graphene (EGR) on choline-functionalized gold nanoparticle (AuNPs-Ch) film. The results of UV-Vis spectra indicated that Tyr retained its original structure in the film, and an electrochemical investigation of the biosensor showed a pair of well-defined, quasi-reversible redox peaks with E(pa) = −0.0744 V and E(pc) = −0.114 V (vs. SCE) in 0.1 M, pH 7.0 sodium phosphate-buffered saline at a scan rate of 100 mV/s. The transfer rate constant k(s) is 0.66 s(−1). The Tyr-EGR/AuNPs-Ch showed a good electrochemical catalytic response for the reduction of CA, with the linear range from 0.2 to 270 μM and a detection limit of 0.1 μM (S/N = 3). The apparent Michaelis-Menten constant was estimated to be 109 μM.