Preparation Of Phytic Acid Metal Complexes, Its Applied Research In Electrochemical Sensors

Electrochemical biosensor is becoming more and more important area of molecular biology and biotechnology. It is becoming more and more significant and valuable for the study of genetic engineering and clinical medicine. But what is the most critical path to construct electrochemical biosensor? The answer must be the method on enzyme immobilization. The structure and properties of the carriers have a great affect on enzyme immobilization. This is why a lot of scholars are dedicated to the study on the material of the carriers.Because nanomaterials have larger BET, more active sites on the external surface and higher capacity, nanotechnology is becoming more and more important for the development of biosensors. Therefore, nanomaterials have been used in great part to construct biosensors to make immobilized enzyme become more effective and reliable. So that biosensors are becoming much more sensitive and powerful. This paper is going to talk about the following three kinds of H2O2 electrochemical biosensor, especially focus on nanotechnology and enzyme immobilization.(1) This chapter is going to construct a simple biosensor by immobilizing horseradish peroxidase (HRP) onto zirconium phytate nanoparticles. Due to the strong chelating ability between phosphates and metal ions, we synthesized a new porous nanomaterials-zirconium phytate by the method of direct precipitation. Further, we tried to employ the nanoporous film of zirconium phytate as a substrate for making the HRP based biosensor by drop-coating method and investigate the electrochemical behavior of enzyme. The UV-vis absorption spectroscopy and electrochemical results showed that the absorbed HRP retained its bioactivity and realized direct electron transfer due to the improved biocompatibility of zirconium phytate. Moreover , the biosensor displayed good bioelectrocatalytic ability toward the reduction of H₂O₂ with a linear response to H₂O₂ over a concentration range from 6.67×10^-7 to 6×10^-6 mol L-1 , and a detection limit of 5.3×10^-7 mol L-1 at a signal-to-noise ratio(S/N)= 3. The Michaelis–Menten constant was estimated to be 1.38 mmol L-1. The biosensor exhibited good reproducibility and stability.(2) Due to the static electricity between ions of opposite charge, we prepared composite films of Zr-IP6/PB by self-assembly technology. The layer of Zr-IP6was fabricated by adsorption of hydrated zirconium from aqueous ZrOCl₂ solution and subsequent reaction with phosphate groups of sodium phytate. The layer of PB nanocrystals was fabricated by sequential adsorption of FeCl₃ solution and K4[Fe(CN)₆] solution. Electrochemical results show that the Zr-IP6/PB composite films show enhanced electrochemical properties in comparison with pure PB films prepared by the multiple sequential adsorption process. Zr-IP6/PB composite films have the capability to catalyze the electrochemical reduction of H₂O₂ with a linear response to H₂O₂ over a concentration range from 2.0×10-5 to 1.76×10-3 mol L-1 and can be used as abiosensor for detecting H₂O₂. (3) Due to the strong chelating ability between phosphates and metal ions, we synthesized a new porous nanomaterials-titanium phytate by the method of microware. Then, we tried to employ the nanoporous film of titanium phytate as a substrate for making the HRP based biosensor by drop-coating method and investigate the electrochemical behavior of enzyme. The UV-vis absorption spectroscopy and electrochemical results showed that this kind of material has a great biological affinity and it can prevent damage to biological activity of enzyme during immobilization. The absorbed HRP realized direct electron transfer and displayed good bioelectrocatalytic ability toward the reduction of H₂O₂ with a linear response to H₂O₂ over a concentration range from 6.67×10^-7 to 4.73×10^-5 mol L-1 , and a detection limit of 4×10^-7 mol L-1 at a signal-to-noise ratio(S/N)= 3. The Michaelis–Menten constant was estimated to be 0.036 mmol L-1. The biosensor exhibited good reproducibility and stability.