A mediator-free phenol biosensor based on immobilizing tyrosinase to ZnO nanoparticles.
A mediator-free phenol biosensor was developed. The low-isoelectric point tyrosinase was adsorbed on the surface of high-isoelectric point ZnO nanoparticles (nano-ZnO) facilitated by the electrostatic interactions and then immobilized on the glassy carbon electrode via the film forming by chitosan. It was found that the nano-ZnO matrix provided an advantageous microenvironment in terms of its favorable isoelectric point for tyrosinase loading and the immobilized tyrosinase retaining its activity to a large extent. Moreover, there is no need to use any other electron mediators. Phenolic compounds were determined by the direct reduction of biocatalytically generated quinone species at -200mV (vs. saturated calomel electrode). The parameters of the fabrication process and the various experimental variables for the enzyme electrode were optimized. The resulting biosensor can reach 95% of steady-state current within 10s, and the sensitivity was as high as 182microAmmol(-1)L. The linear range for phenol determination was from 1.5x10(-7) to 6.5x10(-5)molL(-1) with a detection limit of 5.0x 10(-8)molL(-1) obtained at a signal/noise ratio of 3. In addition, the apparent Michaelis-Menten constant (K(m)(app)) and the stability of the enzyme electrode were estimated. The performance of the developed biosensor was compared with that of biosensors based on other immobilization matrices.
Li
Yin-Feng
YF
State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, People's Republic of China.
Liu
Zhi-Min
ZM
Liu
Yan-Li
YL
Yang
Yun-Hui
YH
Shen
Guo-Li
GL
Yu
Ru-Qin
RQ
D000363:Agaricales / Q000201:enzymology; D015374:Biosensing Techniques / Q000379:methods; D048271:Chitosan; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism*; D014442:Monophenol Monooxygenase / Q000737:chemistry / Q000378:metabolism*; D049329:Nanostructures; D019800:Phenol / Q000032:analysis*; D015034:Zinc Oxide / Q000378:metabolism*
D004800:Enzymes, Immobilized; D019800:Phenol; D048271:Chitosan; D014442:Monophenol Monooxygenase; D015034:Zinc Oxide