title: Porous nanosheet-based ZnO microspheres for the construction of direct electrochemical biosensors.
abstract: Nanosheet-based ZnO microsphere with porous nanostructures was synthesized by a facile chemical bath deposition method followed by thermal treatment, which was explored for the construction of electrochemical biosensors. Spectroscopic and electrochemical researches revealed the ZnO-based composite was a biocompatible immobilization matrix for enzymes with good enzymatic stability and bioactivity. With advantages of nanostructured inorganic-organic hybrid materials, a pair of stable and well-defined quasi-reversible redox peaks of hemoglobin was obtained with a formal potential of -0.345 V (vs. Ag/AgCl) in pH 7.0 buffer. Facilitated direct electron transfer of the metalloenzymes with an apparent heterogeneous electron transfer rate constant (k(s)) of 3.2s(-1) was achieved on the ZnO-based enzyme electrode. Comparative studies demonstrated the nanosheet-based ZnO microspheres were more effective in facilitating the electron transfer of immobilized enzyme than solid ZnO microspheres, which may result from the unique nanostructures and larger surface area of the porous ZnO. The prepared biosensor displayed good performance for the detection of H(2)O(2) and NaNO(2) with a wide linear range of 1-410 and 10-2700 microM, respectively. The entrapped hemoglobin exhibits high peroxidase-like activity for the catalytic reduction of H(2)O(2) with an apparent Michaelis-Menten constant (K(M)(app)) of 143 microM. The nanosheet-based ZnO could be a promising matrix for the fabrication of direct electrochemical biosensors, and may find wide potential applications in biomedical detection and environmental analysis.
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, PR China.
authors.forename: Xianbo
authors.initials: X
authors.lastname: Lu
authors.forename: Haijun
authors.initials: H
authors.lastname: Zhang
authors.forename: Yuwen
authors.initials: Y
authors.lastname: Ni
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhang
authors.forename: Jiping
authors.initials: J
authors.lastname: Chen
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods*; D004563:Electrochemistry / Q000379:methods*; D004566:Electrodes; D005465:Fluorocarbon Polymers / Q000737:chemistry; D006454:Hemoglobins / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000032:analysis; D008863:Microspheres; D049329:Nanostructures; D016062:Porosity; D015203:Reproducibility of Results; D012977:Sodium Nitrite / Q000032:analysis; D017550:Spectroscopy, Fourier Transform Infrared; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D005465:Fluorocarbon Polymers; D006454:Hemoglobins; C040402:perfluorosulfonic acid; D006861:Hydrogen Peroxide; D012977:Sodium Nitrite; D015034:Zinc Oxide