Amperometric Biosensor for Detection of Phenolic Compounds Based on Tyrosinase, N-Acetyl-L-cysteine-capped Gold Nanoparticles and Chitosan Nanocomposite

A novel biosensor was fabricated based on the immobilization of tyrosinase and N-acetyl-L-cysteine-capped gold nanoparticles onto the surface of the glassy carbon electrode via the film forming by chitosan. The NAC-AuNPs (N-acetyl-L-cysteine-capped gold nanoparticles) with the average size of 3.4 nm had much higher specific surface area and good biocompatibility, which were favorable for increasing the immobilization amount of enzyme, retaining the catalytic activity of enzyme and facilitating the fast electron transfer. The prepared biosensor exhibited suitable amperometric responses at -0.2 V for phenolic compounds vs. saturated calomel electrode. The parameters of influencing on the working electrode such as pH, temperature, working potential were investigated. Under optimum conditions, the biosensor was applied to detect catechol with a linear range of 1.0 x 10(-7) to 6.0 x 10(-5) mol center dot L-1 , and the detection limit of 5.0 x 10(-8) mol center dot L-1 (S/N=3). The stability and selectivity of the proposed biosensor were also evaluated.