Nanosheet-based titania microspheres with hollow core-shell structure encapsulating horseradish peroxidase for a mediator-free biosensor

Nanosheet-based titania (TiO2) microspheres with a hollow core-shell structure have been synthesized and employed to immobilize horseradish peroxidase (HRP) in order to fabricate a mediator-free biosensor. The morphology and structure of the TiO2 microspheres were characterized by X-ray diffraction, scanning electron microscopy and transmission electronic microscopy. A possible growth mechanism has been proposed. Spectroscopic and electrochemical measurements revealed that the TiO2 microspheres are an immobilization support with biocompatibility for enzymes, affording good enzyme stability and bioactivity. Due to the nanosheet-based hollow core-shell structure of the TiO2 microspheres, the direct electron transfer of HRP is facilitated and the resulting biosensor displayed good performance for the detection of H2O2, with both a low detection limit of 0.05 mu M and a wide linear range of 0.4-140 mu M, as well as a fast response and excellent long-term stability. The nanosheet-based TiO2 microspheres with hollow core-shell structure, can be used for the efficient entrapment of other redox-active proteins and have wide potential applications in biosensors, biocatalysis, biomedical devices and bioelectronics. (C) 2011 Elsevier Ltd. All rights reserved.