Study On Rapid Food Safety Detection Based On Novel Colorimetric Enzyme Chip And Colloidal Gold Immunochromatographic Assay Strip

In recent years, due to the frequently reported food safety events, people are generally skeptical of the food safety. How to solve the "trust crisis" is a big problem to be solved by the people engaged in food profession. The existing food quality supervision system is generally based on the instrument analysis technology, which is time-consuming and high-costing, and will delay the actual release of information for the food safety determination. So it can not provide the rapid response to the consumer queries. At the same time, due to the distrust in domestic food regulatory system, more and more consumers expect to conduct the determination of food safety by themselves, especially the fast determination of necessary agricultural products. Therefore, there is an urgent need to develop the rapid detection techniques for food safety.This research focused on the food safety problems of pesticide residues and fishery drugs residues, and a colorimetric enzyme chip and a colloidal gold immunochromatographic assay strip were developed.The novel disposable colorimetric enzyme chip was developed for rapid colorimetric detection of pesticide residues in agricultural products, which was based on the inhibition of acetylcholinesterase (AChE) activity by pesticides and the AChE-catalyzed hydrolysis of chromogenic substrate, indoxyl acetate. Through the optimal experiments, the AchE enzyme was directly immobilized onto the Hybond N+nylon membrane by using physical adsorption method. The temperature, time, drying method and volume of enzyme for enzyme immobilization was optimized using the recovery rate of enzyme activity as an indicator, The rate of enzyme activity can reached27.3%after immobilization at4℃for30min and vacuum freeze drying for2min. The color development results of the enzyme chip was blue-green, through the analyses of color intensity changes, the limit of detection (LOD) of this assay system was1μg/mL for omethoate,0.1μg/mL for dichlorvos,2μg/mL for methamidophos,0.05μg/mL for chlorpyrifos,1.5μg/mL for carbaryl, and0.8μg/mL for pirimicarb. Detection results of pesticide residues in real samples of grape and cabbage showed the enzyme chip has high sensitivity, high degree of accuracy, and good reproducibility, suggesting its great potential for practical application in rapid qualitative determination of organophosphorus (OP) and carbamate (CM) pesticide residues in agricultural products.A colloidal gold immunochromatographic assay (GICA) strip was developed for rapid detection of fishery drugs (chloramphenicol, CAP) residues in aquatic products. The NC membrane was used as the carrier, and the polyclonal antibody of CAP as the marker protein. The diameter of colloidal gold nanoparticles was about20nm, the optimal pH and the amount of marker protein were8.0and7.2μg/mL, respectively. The polyclonal antibody of CAP was immobilized onto the conjugate pad after purification. And the antigen (chloramphenicol) and IgG (secondary antibody) were coated onto the NC membrane, followed by blocking the non-specific sites with1%BSA. The LOD of this strip for chloramphenicol detection is1.5ng/mL with great reproducibility. After being stored in4℃for more than90d, the GICA strip still keeps stable properties. The strip provides a potential pathway for rapid detection of CAP in aquatic products.