Preparation Of Polypyrrole Nanomaterials And Its Application In The Detection Of Meat Ingredients

The buying decision of consumers is usually determined by the quality of meat, including tenderness, flavor, color, aroma and juiciness etc., which is related to the concentration and stability of endogenous components. Therefore, how to detect these endogenous components quickly and accurately has received much attention of the researchers. The purpose of this research is to solve the problem that traditional methods could not meet the requirement of protein detection in biological samples. In this paper, the good biological compatibility of polymer nanomaterials were designed and synthesized at the molecular and the nanoscale level using polymer nanomaterials and biological sensing technology, and the biosensor was successfully constructed. In order to quantitatively and quickly detect endogenous components of meat, the electrochemical properties of the biosensor system were tested and analyzed by electrochemical experiments.Polypyrrole (PPy) has attracted much attention because of its high conductivity, environmental stability and ease of synthesizing. The nanoparticles have large specific surface area, high catalytic efficiency, strong adsorption capacity and high surface reactivity. Taking these advantages, strong chemical inertness and optical properties of the UV absorption of PPy materials can be improved by combining nanoparticles. In the thesis, we successfully synthesized PPy-F127 NPs, PPy-Au NPs, PPy-F127-Au NPs based on polypyrrole (PPy), amphiphilic polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) block copolymer (F127) and gold nanoparticles(Au NPs). Based on the electrochemical methods, several rapidly detection methods were established to evaluate some of the most common meat quality indexes (L-lactic acid, myoglobin (Mb), inosine acid (IMP)). The specific contents and results are as follows:1. A novel electrochemical biosensor, which can be conveniently applied to veracious evaluate the level of L-lactic acid with the help of antibiofouling technofogy, was prepared and investigated. More details in preparing of polypyrrole-Pluronic F127 nanospheres (PPy-F127 NPs) and immobilizing lactate oxidase (LOx) on (PPy-F127)/glass carbon electrode (GCE) were presented. And the electrochemical behaviors of the biosensor were studied. The cyclic voltammetric results indicated that LOx immobilized on the PPy-F127 NPs exhibited direct electron transfer reaction, which led to stable amperometric biosensing for L-lactic acid with a detection limit of 0.0088 mM. The regression equation was I (μA)=0.02353 c (mM)+1.4135 (R2= 0.9939). The L-lactic acid biosensor had a good anti-interference property towards uric acid, ascorbic acid, glucose and cysteine. The good stability and repeatability of this biosensor were also proved.2. The PPy-Au NPs was successfully synthesized using a one-step green synthesis method and was characterized by TEM, UV-vis spectroscopy and a diffuse reflectance spectrum. GCEs surface modified with PPy-Au NPs were grafted with MBA, which had excellent binding affinity and selectivity for Mb. The binding of Mb at the modified GCE surface greatly restrained the access of electrons for a redox probe of [Fe(CN)6]3/4-. Moreover, the aptasensor could be used for the detection of Mb in biochemical assays, with a wide detection range (0.0001 to 0.15 g/L) and a low detection limit of 30.9 ng/mL. The aptasensor had a good anti-interference property towards hemin, glucose oxidase, cytochrome c and hemoglobin.3. A bi-enzyme biosensor system for determination of IMP was developed to evaluate the freshness and quality of stored muscles. More details of preparing for PPy-F127-Au NPs and immobilizing bi-enzyme (peroxidase and 5’-nucleotidase) on PPy-F127-Au NPs modified GCE were presented. The electrochemical behaviors of the bi-enzyme biosensor were analyzed, and the concentration of IMP was determined based on the bi-enzyme biosensor response. The results of linear sweep voltammetric (LSV) and square wave voltammetry (SWV) indicated that the catalytic reaction was occurred favorably on the surface of the bi-enzyme biosensor, with a wide detection range (0.05-15 g/L) and a low detection limit of 3.85 ng/mL. The good anti-interference ability, stability and repeatability of this biosensor were also proved. The analytical results by the biosensor system did correlate well with those obtained by liquid chromatography.