Nanoplated bismuth titanate sub-microspheres for protein immobilization and their corresponding direct electrochemistry and electrocatalysis

A layered inorganic perovskite sub-micrometer-scale material, nanoplated bismuth titanate (Bi4Ti3O12) sub-microspheres (NBTSMs) constructed with tens of Bi4Ti3O12 nanoplates, was for the first time synthesized by a facile hydrothermal synthesis strategy. The NBTSMs were employed as a supporting matrix to explore a novel immobilization and biosensing platform of redox proteins through a combined hydrogen bond and electrostatic assembly process. Biocompatibility, stability, reproducibility, and electrochemical and electrocatalytic properties of the resulting NBTSMs-based composite were studied by UV–vis absorption, FTIR, and electrochemical methods. The research results revealed that the NBTSMs-based composite was a satisfying matrix for proteins to effectively retain their native structure and bioactivity. With advantages of the Bi4Ti3O12 layered material, facilitated direct electron transfer of the metalloenzymes with an apparent heterogeneous electron transfer rate constant (ks) of 20.0 ± 3.8 s−1 was acquired on the NBTSMs-based enzyme electrode. The NBTSMs-based biosensor demonstrated significant electrocatalytic activity for the reduction of hydrogen peroxide with an apparent Michaelis–Menten constant (204 μM), wide linear range (2–430 μM), and low detection limit (0.46 μM, S/N = 3). These indicated that the nanoplate-constructed Bi4Ti3O12 sub-microspheres were one of ideal candidate materials for direct electrochemistry of redox proteins and the construction of the related enzyme biosensors, and may find potential applications in biomedical, food, and environmental analysis and detection.