Fabrication Of Fe₃O₄@Au Mimetic Enzyme Electrochemical Enhanced System And Its Application In Food Analysis

In recent years,the safety and quality of food and water is a global issue worthy of attention.According to the survey from the World Health Organization（WHO）,common human illnesses and diseases are fundamentally related to the lack of access to safe drinking water and food.The series of food and water safety issues have prompted the development of highly sensitive,specific and fast analytical techniques for food and water analysis.Electrochemical methods generally meet these criteria while offering additional advantages to achieve excellent accuracy and stability.Recent research results have further demonstrated that this method has potential for real samples analysis of food and water.In addition,inorganic nanomaterials have received increasing attention due to their intrinsic enzyme-like catalytic activities.These nanomaterials mimic enzymes have several unique advantages over their natural counterparts,such as more robust catalytic activities over wide ranges of p H and temperature,more economical production cost,and higher design flexibility through the integration and modification of various functional molecules and nanomaterials.In this research,combining mimic enzymes with electrochemistry,a highly sensitive and selective enzyme-free enhanced electrochemical sensor based on peroxide mimetic enzyme activity of composite nanoparticles was prepared and successfully applied to food analysis and detection.In view of this,the proposed new enzyme-free electrochemical assay has great potential in the fields of food quality control and security detection.（1）The gold magnetic particles（Fe₃O₄@Au）were formed by self-assembling method,its physical and chemical properties are characterized.Then verified the peroxidase-like catalytic activity of the Fe₃O₄@Au with H₂O₂and 3,3’,5,5’-Tetramethylbenzidine（TMB）as substrate and further studies on its catalytic reaction kinetics.The results showed that Fe₃O₄@Au nanometer particles with an average diameter of 150 nm.The saturation magnetization value of Fe₃O₄@Au at 300 K was 46 emu/g.The K_mvalue of Fe₃O₄@Au with H₂O₂as substrate was0.235 mmol/L.Catalytic mechanism analysis suggested the enzymatic kinetics of Fe₃O₄@Au followed the typical Michaelis-Menten mechanism.The as-prepared Fe₃O₄@Au has high affinity to H₂O₂and possessed the excellent peroxidase-like activity.（2）A highly sensitive and selective enzyme-free enhanced electrochemical sensor based on peroxide mimetic enzyme activity of composite nanoparticles（Fe₃O₄@Au）was prepared for the detection of ascorbic acid（AA）.Electrochemical cyclic voltammetry（CV）was used to measure ascorbic acid and the enhanced electrochemical detection system was optimized.The results showed that the established enzyme-free electrochemical sensor showed an extremely high sensitivity towards ascorbic acid under the optimized conditions,with a good linear relationship between the current response and the concentration of ascorbic acid in the range of1 to 100 mmol/L,and then the equation was y=867.81x+3.8608（R²=0.9919）,with a detection limit of 0.0117 mg/L.In addition,the established enzyme-free electrochemical sensor was successfully applied in the detection of ascorbic acid in practical samples.（3）A simple operation enzyme-free enhanced electrochemical sensor based on peroxide mimetic enzyme activity of Fe₃O₄@Au was prepared for the detection of uric acid（UA）.Electrochemical cyclic voltammetry（CV）was used to measure uric acid and the enhanced electrochemical detection system was optimized.The results showed that this enzyme-free enhanced electrochemical sensor showed an excellent electrochemical activity towards the detection of uric acid.Under the optimized experimental conditions the linear dynamic range for the sensing of uric acid was calculated to be 0.1 to 10 mmol/L with the limit of detection of0.0146 mg/L,and the equation was y=13.267x+6.044,coefficient of correlation R²is 0.9952,and then the recovery rate was between 96.17%-105.3%.The established enzyme-free electrochemical sensor showed an extremely high sensitivity and stability towards uric acid under the optimized conditions.（4）A highly stability enzyme-free enhanced electrochemical sensor based on peroxide mimetic enzyme activity of Fe₃O₄@Au was prepared for the detection of dopamine hydrochloride.Electrochemical cyclic voltammetry（CV）was used to measure dopamine hydrochloride and the enhanced electrochemical detection system was optimized.The results showed that a broad linear range of detection（0.01-1 mmol/L）and lower limit of detection（0.0109 mg/L）towards dopamine hydrochloride under the optimized conditions,and then the recovery rate was 94.56%-115.28%.This enzyme-free enhanced electrochemical sensor showed excellent sensitivity for dopamine with good reproducibility.Further,the detection of dopamine hydrochloride in meat sample analysis was performed successfully with satisfactory the recovery of standard addition.（5）A highly specificity enzyme-free enhanced electrochemical sensor based on peroxide mimetic enzyme activity of Fe₃O₄@Au was prepared for the detection of catechol（CC）.Electrochemical cyclic voltammetry（CV）was used to measure catechol and the enhanced electrochemical detection system was optimized.The results showed that a good linear relationship was observed from 0.001 to 0.1 mmol/L and the limit of detection was calculated as 1.638μg/L towards dopamine hydrochloride under the optimized conditions,and the recovery rate was 97.10%-108.10%,meanwhile,it had certain anti-interference ability.This enzyme-free enhanced electrochemical sensor showed excellent sensitivity and selectivity for dopamine.Furthermore,the detection of catechol in drinking water analysis was performed successfully with satisfactory the recovery of standard addition.