An enzyme immobilization platform for biosensor designs of direct electrochemistry using flower-like ZnO crystals and nano-sized gold particles

A novel immobilization platform has been developed for fabricating enzyme-based biosensors of direct electrochemistry by synergistically using ZnO crystals and nano-sized gold particles (Nanogold). ZnO crystals were synthesized with flower-like structure to be casted on the electrode mediated by chitosan so as to provide larger surface area for anchoring horseradish peroxidase (HRP)-labeled Nanogold. The resultant enzyme biosensor was tested for the determination of H2O2 as a model of test system. Experimental results showed that HRP could be immobilized onto the nanocomposite matrix with high loading amount and well-retained bioactivity. Moreover, rapid and direct electron transferring could be achieved between the enzyme's active sites and the electrode surface, thus facilitating the direct electroanalysis of H2O2. The developed enzyme sensor can directly determine H2O2 in the concentration range from 1.5 x 10(-6) to 4.5 x 10(-4) M, with a detection limit of 7.0 x 10(-7) M. High detection reproducibility can be additionally expected. Such an enzyme immobilization platform of ZnO-Chitosan/Nanogold should hold great promise for the development of the enzyme biosensors of direct electrochemistry. (C) 2008 Elsevier B.V. All rights reserved.