Construction Of Electrochemical Sensors Based On Gold Nanomaterials And Evaluation Of Parameters Related To Meat Quality And Safety

Meat quality includes flavor,color,the concentration of protein,purine,preservative in meat and microbial indicators.With the improvement of people's living standard,meat quality and safety have been paid more and more attention.Gout is an auto-imflammatory disease which ascribed to the chronic increase of uric acid caused by the disorder of purine metabolism.Purines mainly include adenine(A),guanine(G),xanthine(X)and hypoxanthine(HX).Nitrite has always been used as a food additive,which can cause damage to the human body.Salmonella is an important zoonotic pathogens,and has been widely prevalent in animals,food and breeding environment.In this study,convenient,rapid and accurate methods for detection of purines,nitrites and Salmonella were established for evaluation the quality and safety of meat products.Due to the highly specificity,good sensitivity and biocompatibility,gold nanoparticles(Au NPs)has been widely used in sensor.Herein,the Au-based nanocomposite materials(gold nanoparticles-polypyrrole-graphene oxide composite material(Au-PPy-GO),manganese dioxide-gold nanoparticle composite material(MnO₂-Au)and molybdenum disulfide-polyaniline-gold nanoparticle composite material(Mo S₂-Pani-Au))were prepared,and the electrochemical sensors were constructed based on the nanocomposite materials.The integration of the technologies,which include nanocomposite material and sensor,will have significant input to interest for human health.The main results can be concluded as follows:(1)A novel electrochemical sensor based on Au-PPy-GO nanocomposite material was fabricated and used for detection of purines.Au-PPy-GO nanocomposite was prepared by an one-step method and characterized by transmission electron microscopy(TEM),X-ray diffraction(XRD),Raman spectroscopy(Raman)and infrared spectroscopy(FTIR).The Au-PPy-GO/GCE electrochemical sensor was established to detect purines at the same time.In order to improve the electrochemical response of the sensor,cyclic voltammetry(CV)was used to modify 1-octyl-3-methylimidazole hexafluorophosphate(OMIMPF₆)on the surface of the sensor.Meanwhile,xanthine oxidase(XOD)was added into the buffer and used as catalyst.After that,xanthine and hypoxanthine are catalyzed and oxidized to uric acid,resulting varied in the peak currents and the peak voltage.Differential pulse voltammetry(DPV)was used to quantitatively detect purines.The detection ranges of A,G,HX and X were respectively:0.5?200?M,0.1?200?M,1?200?M and 0.001?160?M,and the detection limits were 110.4 n M,30.9 n M,99.8 n M and 99.8 n M,respectively.The good selectivity,stability and repeatability of this sensor were also proved.Importantly,the results of the detection of purines in practical chicken broth were well consistent with the data determined by high performance liquid chromatography(HPLC).(2)Electrochemical nitrite sensor was constructed based on MnO₂-Au nanocomposite material and its applicationMnO₂-Au nanocomposite was prepared,and the nanocomposite was characterized by TEM,XRD,Raman and FTIR.The results indicated the nanocomposite had good conductivity and catalytic activity.The MnO₂-Au/GCE electrochemical sensor was established to detect nitrite.In order to obtain better electrochemical signals,the experimental methods(differential pulse voltammetry,square wave voltammetry and linear sweep voltammetry)and experimental conditions(p H,concentration and volume of MnO₂-Au)were optimized.DPV was used to quantitatively detect nitrite,and the detection range was 0.1?1000?M,the detection limit was 0.029?M.Meanwhile,the anti-interference experiment proved that the method has good selectivity and anti-interference to nitrite.The standard addition method was used to detect a variety of actual samples(chicken breast,sausage,cured duck leg and cured pork).The recovery rate measured by the sensor was 99.46%?102.11%,and the RSDs were less than 6%.More importantly,the obtained results was similar to that of UV method.The results showed that the method has high accuracy and could be used for detection of nitrite in meat.(3)An electrochemical sensor based on Mo S₂-Pani-Au nanocomposite material and and its application in Salmonella inv A gene fragment.Mo S₂-Pani-Au nanocomposite was prepared,and was characterized by TEM,XRD,Raman and FTIR.Then,the Mo S₂-Pani-Au/GCE electrochemical sensor was successfully established.The Inv A gene fragment is unique to Salmonella.Therefore,an Aptamer/Mo S₂-Pani-Au/GCE sensor that can be used for detection of Salmonella was constructed by modifying the aptamer of the Inv A gene fragment on the electrode surface.In order to obtain better electrochemical signals,the experimental methods(differential pulse voltammetry,square wave voltammetry and linear sweep voltammetry)and experimental conditions(p H,the volume of MnO₂-Au,and the incubation time of the aptamer and inv A)were optimized.DPV was used to quantitatively detect nitrite,the detection range was 0.01?750 p M,and the detection limit was 0.005 p M.By changing the base pair of the inv A gene fragment to obtain the interference gene.It was found that the Aptamer/Mo S₂-Pani-Au/GCE sensor had no obvious electrochemical signal change.Experimental results showed that the sensor could be applied to the rapid detection of Salmonella in meat products,and this method had a good application prospect.