Hydroxyl-containing antimony oxide bromide nanorods combined with chitosan for biosensors

A hydroxyl-containing antimony oxide bromide (AOB) nanorods was synthesized by a hydrothermal method. TEM and SEM images showed that the as-prepared AOB nanorods were very copious with diameters of about 50 nm. The AOB nanorods could be easily combined with biopolymer chitosan (Chi) to form an organic–inorganic hybrid material, and a biocompatible, crack-free and porous Chi–AOB composite film could be readily obtained. Horseradish peroxidase (HRP) was chosen as a model protein to construct a reagentless mediator-free third-generation HRP biosensor. UV–visible and FTIR spectroscopy revealed that HRP entrapped in the composite film could retain its native secondary structure. A pair of stable and well-defined redox peaks of HRP with a formal potential of about −0.24 V (vs. Ag/AgCl) in a pH 7.0 phosphate-buffered solution (PBS) were obtained at the HRP–Chi–AOB composite film modified glassy carbon (GC) electrode. With advantages of organic–inorganic hybrid materials, dramatically facilitated direct electron transfer of HRP and excellent bioelectrocatalytic activity towards H2O2 were demonstrated. The apparent Michaelis–Menten constant KMapp was calculated to be 7.5 μm, indicating that HRP entrapped in the composite film possessed high affinity to H2O2 and exhibited high enzymatic activity. The prepared biosensor displayed good sensitivity and reproducibility, wide linear range, low detection limit, fast response and excellent long-term stability. The Chi–AOB composite film could be used efficiently for the entrapment of other redox-active proteins and may find wide potential applications in biosensors, biocatalysis, biomedical devices and bioelectronics.