Study On Novel Nanocomposites Based Electrochemical Hydrogen Peroxidase Sensors

Hydrogen peroxide is not only a by-product of several highly selective oxidases, but also an essential mediator in environmental, industrial, biological, food and clinical analysis. Therefore the rapid and accurate analysis of H2O2is of great importance in many fields including industry, biotechnology, food testing, clinical diagnostics and other fields. Conventional techniques such as titration analysis, fluorescence, high performance liquid chromatography, colorimetry, spectrophotometry, chemiluminescence and electrochemical method have been reported in literatures. Among them, electrochemical enzyme sensor is widely used in qualitative and quantitative analysis with simple, selective and high sensitivity to hydrogen peroxide. In this dissertation, three kinds of HRP electrochemical sensors based on carbon nanotubes, graphene and gold nanoparticle are proposed, and these electrochemical sensors could transfer electron directly, owing to the special properties of these nanomaterials. The detail contents are described as follows:1. Sodium alginate is biocompatible, carbon nanotubes can promote direct electron transfer of enzyme protein on the electrode surface, and moreover, alginate has good capacity in dispersion of carbon nanotubes. In this paper, the HRP are fixed to the SA-MWCNT/GC electrode surface by covalent bond. The results show that HRP can transfer electron directly and effectively, and the direct electron transfer rate constant (Ks) is0.621±0.0581s-1, Further experiments showed that the sensor has a smaller Michaelis constant (Km=1.874mM), a good linear relationship with H2O2in the ranges from2.0×10-4to2.2×10-3M. The detection limit was estimated to be6.6×10-6M at a signal-to-noise ratio of3.2. The biocompatible composite film alginate-graphene (SA-GR) is fixed to the electrode surface, and then HRP is immobilized on the SA-GR membrane through an amide bond, thereby a good performance hydrogen peroxide biosensor is prepared. HRP immobilized on the electrode surface has a quasi-reversible electrochemical reactions in PBS buffer. It indicates that SA-GR composite material can promote the direct electron transfer of HRP and has good biocompatibility. The HRP biosensor has high sensitivity, good reproducibility, fast response (3s), low Michaelis constant (Km=0.663) and a good linear relationship with H2O2in the range from1.0×10-4to1.2×10-3M. The detection limit was estimated to be5.7×10-6M at a signal-to-noise ratio of3.3. Gold nanoparticles (AuNPs) own good biocompatibility and can well adsorb proteins. Based on these outstanding properties of AuNPs, we construct a new type of hydrogen peroxide biosensor. We first fixed the biocompatible SA-MWCNT composite membrane on the electrode surface, and the SA-MWCNT electrode was then modified with AuNPs. Finally, HRP was immobilized on the AuNP-SA-MWCNT composite film, and a good performance of the electrochemical biosensor for hydrogen peroxide was successfully prepared. This sensor has high sensitivity, good reproducibility, low Michaelis constant(Km=0.288) and a good linear relationship with H2O2in the ranges from1.0×10-4to0.8×10-3M. The detection limit was estimated to be2.96×10-5M at a signal-to-noise ratio of3.