Optical Aptasensors For The Determination Of Phorate And Isocarbophos In Vegetables

Organophosphorus pesticides are widely used in pest control,but they are extremely toxic to organisms,cause neurological diseases and even death due to the inhibition of acetylcholinesterase.Many countries and organizations have legislated to strictly control the residues of organophosphorus pesticides in food,drinking water and the environment.Therefore,rapid screening and accurate quantification of organophosphorus pesticides is particularly important.Due to the high sensitivity and simple operation of optical sensors,the development of new optical sensors for the determination of organophosphorus pesticides is conducive to improving food safety and promoting the development of food analysis technology.The main contents are as follows:?1?A fluorescent aptasensor based on 6-carboxyfluorescein?FAM?and gold nanoparticles?AuNPs?was fabricated for the determination of phorate residue in vegetable samples.FAM-labeled phorate aptamer?FAM-aptamer?was used as fluorescent donor and sodium citrate-reduced AuNPs as fluorescent receptor to fabricate a fluorescence resonance energy transfer?FRET?based aptasensor.In the absence of phorate,the fluorescence of FAM-aptamer was quenched due to the adsorption of single-stranded DNA?aptamer?to AuNPs and high-efficiency FRET process.In the presence of phorate,the aptamer bound to the phorate and left the surface of AuNPs,and FRET was inhibited.Under the optimal conditions,there was a linear response between the change of fluorescence intensity and the phorate concentration from 0.5to 5 mg/L with the linear regression equation of y=53.90x+5.212?R²=0.9944?and the detection limit of 0.27 mg/L.The recoveries of phorate were in the range of 93.5%?112.4%,and the relative standard deviations?RSDs?were 6.5%?11.3%.The aptasensor was applied for the determination of phorate in vegetable samples with good selectivity.?2?A colorimetry-phosphorescent dual-modal aptasensor was fabricated and applied to the determination of isocarbophos pesticide in vegetable samples.The aptamer bound to the isocarbophos and left the surface of AuNPs,and the AuNPs aggregated in high-salt solution without the protection of the aptamer.The color of solution changed from red to blue and the maximal absorption wavelength is red-shifted,so a colorimetric method for the determination of isocarbophos was established.Amino-functionalized Zn₂GeO₄:Mn persistent luminescence nanorods?PLNRs-NH₂?were prepared by hydrothermal method and hydrolytic polymerization of 3-aminopropyl-triethoxysilane.PLNRs-NH₂ was used as phosphorescent donor and AuNPs as phosphorescent quencher.Due to the internal filtration effect between AuNPs and PLNRs-NH₂,the dispersed AuNPs have a strong quenching effect on the phosphorescence of PLNRs-NH₂,while the quenching effect of aggregated AuNPs induced by isocarbophos on phosphorescence was much weaker.So,a phosphorescent method for the determination of isocarbophos was developed.The colorimetric mode gave a linear response between the absorption ratio at 620 nm and 520 nm(A₆₂₀/A₅₂₀)and the isocarbophos concentration from 50?g/L to 500?g/L with the linear regression equation was y=0.0022x+0.4299?R²=0.9935?and the detection limit of 7.1?g/L.The phosphorescent mode offered a linear response between the change of phosphorescence intensity at 537 nm and the isocarbophos concentration from 5 to160?g/L with the linear regression equation was y=2.648x+12.78?R²=0.9912?and the detection limit of 0.54?g/L.The developed method was applied for the determination of isocarbophos in Chinese cabbage,spinach and lettuce samples with the recoveries of 101.7%?108.8%and the RSDs of 1.0%?5.7%.In this paper,the developed fluorescent aptasensor had the advantages of simple preparation,less sample pretreatment steps,good specificity and sensitivity,and could be used for the determination of phorate in vegetable samples.In addition,a colorimetric-phosphorescent dual-modal aptasensor was developed.The colorimetric mode could be used for semi-quantitative determination of isocarbophos by naked eye observation,while the determination of isocarbophos in phosphorescent mode gave improved signal-to-noise ratio and sensitivity by eliminating background interference.The phosphorescent mode was innovatively applied in the determination of isocarbophos in vegetable samples with high specificity and sensitivity.