Direct electrochemistry of myoglobin immobilized on chitosan-wrapped rod-constructed ZnO microspheres and its application to hydrogen peroxide biosensing

Rod-constructed zinc oxide (ZnO) microspheres (RZnOMs), consisting of hundreds of needle-like ZnO nanorods, were utilized to explore a novel biosensor through coupling with myoglobin (Mb) in the presence of chitosan (Chi). Biocompatibility and electrochemical properties of the resulting ZnO-Chi-Mb composite film were studied by Fourier-transform infrared spectroscopy and cyclic voltammetry. The results revealed that the RZnOMs-based composite was a satisfying matrix for proteins to effectively retain their native structure and bioactivity. With advantages of the unique inorganic material, facilitated direct electron transfer of the metalloenzymes was acquired on the RZnOMs-based enzyme electrode. Moreover, the RZnOMs-based biosensor also displayed significant electrocatalytic activity for the reduction of hydrogen peroxide with an apparent Michaelis-Menten constant (32 A mu M), wide linear range (2-490 A mu M), and low detection limit (0.21 A mu M, S/N = 3). These indicated that the RZnOMs were one of the ideal candidate materials for direct electrochemistry of redox proteins and related biosensor construction.