Preparation Of Gold Magnetic Particles And Application Of Mimic Enzymes Properties On Food Analysis And Detection

With the continuous development of food processing industrialization,people's requirements for the nutrition and quality of food are getting higher and higher.Therefore,it is necessary to improve and innovate the food safety detection technology of food composition determination to ensure food quality.Conventional analytical methods are limited by instruments,high costs and cumbersome operation.In recent years,the real-time detection with colloidal gold,inorganic nanoparticles,upconversion chemiluminescent materials as carriers has become a research hotspot in the field of analysis and detection because of its time and space advantages that laboratory does not have.However,traditional enzyme biosensor detection technology mostly depends on the activity of natural enzyme markers,and its use and storage are affected by environmental factors such as pH and temperature.At present,chemiluminescence analysis and colorimetric sensing methods based on the properties of inorganic nanomaterials mimic enzymes have developed rapidly,which have solved some inherent shortcomings of natural enzymes.In addition,compared with chromatographic analysis and electrochemical methods,quantitative detection based on visual detection and ultraviolet spectroscopy has realized miniaturization of the instrument,simplified operation methods and intuitive results,and more suitable for the instant detection of the samples.In this study,composite nanoparticles with good dispersibility and stability were prepared,and their synergistic effects further enhanced the activity of peroxidase-like enzymes,and their simulated enzymatic reaction process was explored.On this basis,its application in food analysis and detection was studied by its peroxidase-like properties(1)Fe3O4 nanoparticles were rapidly prepared by hydrothermal method,the gold magnetic particles(GoldMag)were synthesized by the Fe3O4 nanoparticles combined with gold nanoparticles prepared by green reduction using self-assembly method based on the surface amino groups,The preparation process of gold magnetic particles was optimized and their properties were characterized.The results show that aminated Fe3O4 nanoparticles can effectively immobilize gold nanoparticles.GoldMag has been successfully constructed based on self-assembly method.The optimum process combination was as follows:the addition of Fe3O4 suspension was 2 mL,the temperature was 60?,and the time was 60 min.The saturation magnetization of GoldMag is 41 emu/g,and and showed strong catalytic properties.(2)The catalytic activity of GoldMag peroxidase-like was investigated,and its catalytic reaction conditions were optimized,and the stability and reusability of its peroxidase mimetic enzyme were investigated.The kinetics of enzymatic steady-state reaction and the possible catalytic mechanism were also explored.The results showed that GoldMag could catalyze the reaction of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)(ABTS)with hydrogen peroxide to produce color reaction.The Km value is 0.51.The catalytic mechanism of GoldMag peroxidase activity was investigated by electrochemical means.The results showed that the possible catalytic mechanism of GoldMag peroxidase activity was that it accelerated the electron transfer between the chromogenic substrate and the oxygen adsorbed on its surface.The synthesized GoldMag exhibits good catalytic activity,higher stability and peroxidase specificity than natural enzymes.(3)The glucose detection system was constructed by using GoldMag peroxidase-like activity.Glucose with glucose oxidase(GOx)to produce H2O2 and to produce the color reaction with ABTS.Based on this principle,a simple and highly sensitive,highly selective and visualized method for the determination of glucose content was established.Under optimum conditions,glucose has a good linear relationship in the range of 1 mmol?20 mmol/L,the linear correlation coefficient R2 value is 0.9925,the detection limit is 2.45 ?mol/L,the recovery rate was between 96%-104%,and showed good sensitivity,selectivity and stability.(4)The ascorbic acid detection system was constructed by using GoldMag peroxidase-like activity.GoldMag can be used to catalyse oxidation of the peroxidase substrates 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid)(ABTS)produce a green-colored product in presence of hydrogen peroxide.Ascorbic acid as an effective antioxidant have scavenging effects on ABTS radicals and induce the reduction of green ABTS+to colorless ABTS2-,resulting in a significant green color fading.On this basis,a rapid,sensitive and selective colorimetric assay for ascorbic acid has been developed.Under optimal conditions,ascorbic acid has a linear response range from 0.01 mmol to 1 mmol/L with a detection limit of 0.12 ?mol/L and a short assay time of the 30 s.The method has been successfully applied to the determination of ascorbic acid in practical samples.The recovery of ascorbic acid is between 96%-106%.The colorimetric detection system showed good sensitivity,selectivity and stability.(5)The cholesterol detection system was constructed by using GoldMag peroxidase-like activity.GoldMag can be used to catalyse oxidation of the peroxidase substrates 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid)(ABTS)produce a green-colored product in presence of hydrogen peroxide.A colorimetric method for visual detection of cholesterol was established by combined with the principle that cholesterol produces H2O2 under the action of cholesterol oxidase to produce the color reaction with peroxidase substrate ABTS.Cholesterol has a good linear relationship in the range of 0.1-7.5 mg/mL.The linear correlation coefficient R2 value is 0.9913,and the detection limit is 0.003 mg/mL.The method has been applied to the detection of real samples.The recovery rate of standard addition was between 96%-104%,and showed good sensitivity,selectivity and stability.