Development And Application Of New Test Strips For Rapid Detection Insecticide Residues

Compared to the confirmatory analyses via chromatographic means, the enzyme-inhibited and immunological methods for rapid detection of insecticide residues have been widely used for food safety control in some developing countries. Among of those typed analyses, acetylcholinesterase (AChE)-based test strips are involved in the standard method in China (GB/T 5009.199).Unfortunately, the current test strips have some drawbacks, such as temperature control, depending on manually fold the enzyme piece and substrate piece and inadequacy of the reaction between enzyme and substrate, which directly lead to complicated operation procedure and false results.In this study, we developed one new test strips, with the obtained recombinant Drosophila melanogaster AChE (R-DmAChE) carrying high sensitivity and stability in our group before. The substrate and visual color change and design were optimized. Then, enzyme or substrate immobility, immobility condition of the enzyme, optimum quantity of the enzyme and substrate, reaction time between enzyme and substrate, coloring reaction time were serially studied. Finally, detection time, sensitivity and stability of these new test strips were evaluated.The experimental results showed that design of the rapid strip change into horizontal, and the biochemical reaction can be carried out in the liquid environment. The hydrolysate of colorless substrate 3-indoxyl acetate is oxidized to blue colored Indigo, which was suitable as coloring reagent for visual color detection by naked eyes. Negative sample is colorless, whilst positive sample is blue. The quantity of the AChE was 3 U, the concentration of agar was 0.6%, the quantity of 3-indoxyl acetate was 4 mg.3μg/L of dichlorvos, 50μg/L of carbosulfan, 10μg/L of dipterex and 0.4 mg/L of omethoate enable to effectively inhibit the enzymatic activity of AChE. In addition, the stability of these test strips will remain after 16 weeks during storage at 4℃.Overall, compared to the similar type of Tianhe lvzhou, the newly developed test strips have better performance on easy operation, low cost and high sensitivity, which have the great potential to apply for rapid detection of pesticide residues.