The Preparation Of The Nanocomposite Materials And Their Application In The Electrochemical Biosensors

As electrochemical enzyme biosensors have the advantages of high-sensitivity, high-selectivity as well as easy miniaturization, they have gained wide attention and made much more progress. It is reported that the crucial aspect in the fabrication of a biosensor is the immobilization of bio-recognition molecule. Nano-composite materials, exhibiting large specific surface area, strong adsorption capacity, high catalytic activity and good biocompatibility, are favorable for constructing biosensors, which not only retain the biological activities of biomolecules, but also enhance the performance of the biosensors. In this thesis, nano-composite materials with different morphologies were synthesized by the various methods and employed to construct the electrochemical enzyme biosensors. The fabricated biosensors for glucose and cholesterol showed wide linear range, high sensitivity, low detection limit and rapid response. The main works and conclusions are included as follows:1. Glucose biosensor based on prussian blue-gold nanocomposite filmsA glucose biosensor was developed, which was based on prussian blue-gold (PB-Au) nanocomposite films and platinum nanoclusters (Pt-NCs). Prussian blue (PB), as an electron mediator, was electrochemically deposited on the glass carbon electrode (GCE) in the presence of chloroauric acid, forming PB-Au nanocomposite films. Then, Pt-NCs were electrodeposited to construct a bilayer film. At last, glucose oxidase (GOD) was modified on the electrode with the bilayer film and the film of Nafion was used to prevent GOD from leaking off. The resulting amperometric glucose biosensor exhibited a fast response time (within 8 s) and a linear calibration range from 3.0μmol/L to 1.1 mmol/L with a low detection limit of 1.0μmol/L glucose (S/N=3). With the low operating potential, the biosensor showed little interference to the possible interferents, including acetum acid, uric acid and arginine, indicating an excellent selectivity.2. The construction of glucose biosensor based on platinum nanoclusters-multiwalled carbon nanotubes nanocomposites One-step synthesis method was proposed to obtain the nanocomposites of platinum nanocluster and multiwalled carbon nanotubes (PtNCs-MWCNTs), which were used as a novel immobilization matrix for the enzyme to fabricate the glucose biosensor. The whole fabrication process of the biosensor was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM) and scanning electron microscope (SEM). Due to the favorable characteristic of PtNCs-MWCNTs nanocomposites, the biosensor exhibited good characteristics, such as wide linear range (3.0μmol/L-12.1 mmol/L), low detection limit (1.0μmol/L), high sensitivity (12.8μA L/mmol), short response time (within 6 s). Finally, it was demonstrated that this biosensor can be used for the assay of glucose in human serum samples. The performance of the resulted biosensor was more prominent than that of most of the reported glucose biosensors.3. The preparation of the biocomposite film by the method of one-step electrodeposition and its application in the cholesterol biosensorWe reported an ingenious approach for the fabrication of a promising cholesterol biosensor, which integrated the beneficial characteristics of multiwalled-carbon nanotubes (MWCNTs), gold-platinum alloy nanoparticles (Au@PtANPs) and chitosan (CS). Cholesterol oxidase (ChOx) was immobilized via glutaraldehyde as a cross-linker onto CS-MWCNTs-Au@PtANPs nanobiocomposite film deposited onto glassy carbon electrode. Scanning electron microscopy (SEM) images of CS-MWCNTs-Au@PtANPs revealed that MWCNTs and Au@PtANPs were dispersed in CS matrix. Cyclic voltammetry and impedance spectroscopy were used to characterize the assembly process of the biosensor. The proposed biosensor exhibited a linear current response to glucose concentration (0.7～477.7μmol/L) at the potential of 0.5 V. The sensitivity to the change in the concentration of cholesterol as the slope of the calibration curve was 224.5μA L/mmol.4. Highly-sensitive cholesterol biosensor based on platinum-gold hybrid functionalized ZnO nanorodsA novel scheme for the fabrication of gold/platinum hybrid functionalized ZnO nanorods (Pt-Au@ZnONRs) and multiwalled carbon nanotubes (MWCNTs) modified electrode was presented and its application for cholesterol biosensor was investigated. Firstly, Pt-Au@ZnONRs was prepared by the method of chemical synthesis. Then, the Pt-Au@ZnONRs suspension was dropped on the MWCNTs modified glass carbon electrode, and followed with cholesterol oxidase (ChOx) immobilization by the adsorbing interaction between the nano-material and ChOx as well as the electrostatic interaction between ZnONRs and ChOx molecules. The combination of MWCNTs and Pt-Au@ZnONRs provided a favorable environment for ChOx and resulted in the enhanced analytical response of the biosensor. The resulted biosensor exhibited a linear response to cholesterol in the wide range of 0.1-759.3μmol/L with a low detection limit of 0.03μmol/L and a high sensitivity of 26.8μA L/mmol. The calculated apparent Michaelis constant Km was 1.84 mmol/L, indicating a high affinity between ChOx and cholesterol.