title: A mediator-free phenol biosensor based on immobilizing tyrosinase to ZnO nanoparticles.
abstract: 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.
authors.affiliation: State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, People's Republic of China.
authors.forename: Yin-Feng
authors.initials: YF
authors.lastname: Li
authors.forename: Zhi-Min
authors.initials: ZM
authors.lastname: Liu
authors.forename: Yan-Li
authors.initials: YL
authors.lastname: Liu
authors.forename: Yun-Hui
authors.initials: YH
authors.lastname: Yang
authors.forename: Guo-Li
authors.initials: GL
authors.lastname: Shen
authors.forename: Ru-Qin
authors.initials: RQ
authors.lastname: Yu
mesh_terms: 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*
chemical_list: D004800:Enzymes, Immobilized; D019800:Phenol; D048271:Chitosan; D014442:Monophenol Monooxygenase; D015034:Zinc Oxide