Array Type Multi-Layer Paper-Based Microfluidic Chip Pesticide Detection Method

In recent years,the fruit yield and vegetable planting area in China have increased year by year.At the same time,the amount of pesticide used is proportional to the yield of fruit and vegetable.The pesticide residues in fruits and vegetables are between ?g/kg to mg/kg,and there are many kinds of pesticides.Therefore,it is necessary to realize the rapid,low-cost and visual specific detection of agricultural pesticide residues.In this paper,an array paper-based microfluidic chip with high sensitivity,which can realize the specific detection of two pesticides,was designed from two aspects: fluorescence specific detection based on aptamers and high-efficiency mixed structure design.The research contents and results of the study are summarized as follows:(1)A fluorescence detection method for pesticide residues was constructed by combining the aptamer which can identify the target pesticide with the gold nanoparticles(AuNPs)-quantum dots(CdTe QDs)system based on inner filtration effect(IFE).Gold nanoparticles and green quantum dots were prepared and characterized.The maximum absorption peak of AuNPs was at 520 nm and the maximum emission peak of CdTe QDs was at 535 nm.The absorption spectrum of AuNPs overlapped with that of CdTe QDs.The specific binding of acetamiprid and aptamer affected the aggregation and dispersion of AuNPs in NaCl solution.The high sensitivity of pesticide residue detection was attributed to IFE effect,and it was confirmed that the quenching of CdTe QDs by AuNPs was only affected by IFE.Finally,the fluorescence responses of different acetamiprid concentrations(0?M,0.5?M,1?M,3?M,5?M,7?M)in the AuNPs-NaCl-aptamer-CdTe QDs system were measured,and it was found that acetamiprid was linearly related to the fluorescence growth rate in the range of 0.5~7 ?M.(2)The promoting effect of the mixed channel structure on the mixed effect is analyzed.Based on the design idea of forcing the fluid layer to stretch,fold,divide and merge to strengthen mixing,three types of mixed structures were designed,namely,three types of pipe wall barrier structures(semi-circular staggered structure,truncated circular staggered structure and circular stacked structure)were designed according to the design idea of forcing the fluid layer to stretch and fold to enhance mixing.The design idea of forcing fluid layers to be divided and combined to enhance mixing was to design two kinds of internal barrier structures(circular barrier mixing and square barrier mixing);And a composite structure designed by combining the above two ideas.COMSOL is used to simulate each geometric parameter of each structure of each type one by one,and the mixing intensity value le is defined to evaluate the mixing effect of each structure.The simulation results show that the micro-mixing channel of "d2-1700?m,type" structure has the best mixing effect,the Ie value was 0.92441,and the improvement rate compared with the blank control group was 231.698%.Finally,the truncated circle staggered structure was selected as the mixing structure of the paper chip mixing area.(3)The results of simulation optimization were tested by color developing agent,and the simulation results were confirmed by color analysis of its mixing effect.Based on the fluorescence detection method and the optimal mixing zone channel,an array paper-based sensor capable of simultaneously detecting two pesticides is designed.The sensor can semi-quantitatively judge pesticide residues by the difference in fluorescence intensity between the pesticide detection zone and the control zone.The results show that the detection range of acetamiprid by this detection system was 50 ~ 600? g/kg.The detection range of propylbromide was 60 ~480?g/kg,which was lower than the maximum residue limit of pesticides in the national standard.The paper-based array fluorescence pesticide residue detection sensor has high sensitivity,and has the specificity detection for two or more pesticides at the same time,and provides methods for accurate detection of multiple targets in food and environmental safety.