Silk Based Enzyme Inhibition Biosensor For Organophosphorus Pesticide And Aflatoxin B1 Detection

The issue of food safety has become a global topic.Acute poisoning caused by excessive levels of pesticide residues in vegetables and fruits,as well as excessive levels of aflatoxins in milk and dried fruits,etc.have seriously affected the development of the food industry in China.Therefore,it is necessary to effectively detect the residual amount of these harmful substances in food.In this paper,different methods of membrane formation of silk fibroin were used to embed acetylcholinesterase,and the effects of silk fibroin on the long-term maintenance and stabilization of acetylcholinesterase activity under different temperature conditions were tested.The substrate acetylcholine(ACh)is hydrolyzed by acetylcholinesterase(ACh E)to form choline and acetic acid,which decreases the p H of the solution.Organophosphorus and carbamate pesticides and aflatoxin have inhibitory effects on acetylcholinesterase.When pesticides and AFB1 are added,the activity of ACh E is inhibited,and thus the hydrolysis of the substrate is inhibited,the acetic acid produced is reduced,and the p H value of the solution is will pick up.In this paper,silk fibroin is used for the protection of acetylcholinesterase,silk fibroin is used as an effective carrier,and the embedding of acetylcholinesterase and p H test paper is realized at the same time.The biosensor can still effectively detect the pesticide content after being stored at 37°C for 180 days.Compared with the commercially available pesticide speed test card,the biosensor has a significant improvement in the stability;the detection limit of paraoxon is 6.57 ppb,and aldicarb is 8.92 ppb and AFB1 was 0.274 ppb.In addition,it has been succesully applied to the testing of actual samples(Chinese cabbage and peanuts),demonstrating that the sensor can guarantee good sensitivity and stability,and has the potential for practical detection applications.On the basis of the significant improvement in stability,in order to improve sensitivity,by screening color reagents,it was found that the detection limit of quantum dots as a color developing agent can reach 0.98 ppb,which is lower than the detection limit of p H indicator paper as a color developer.In addition,using silk fibroin and PAH optimized for screening as carriers,based on the electrostatic binding of them,combined with layer-by-layer self-assembly techniques,enzymes,substrates,and color reagents were directly constructed in one system.On the one hand,the sensitivity is improved by optimizing the number of coatings and shortening the response time.On the other hand,greater possibilities are provided for the practical application of the biosensor.