The Development Of Dual Colormetric And Fluorecent Assay For Organophosphate Pesticides And Ractopamine Using Gold Nanoparticles

Organic Agriculture and food safety are inseparable from people's daily life.Due to high-rate occurrences of food safety issues,traditional analysis method cannot meet the security detection requirement of agricultural products and food.Therefore,there is increasing demand to develop simple and fast food quality detection method with high sensitivity and precision in the area of agriculture and food safety.Due to its unique quantum effect,Gold nanoparticles?AuNPs?possesses strong capacity of signal generation and transduction,which make AuNPs the most potential material of high development and application value in the qualitative and quantitative analysis.AuNPs are simple to prepare,have various signal characterization methods,and are fast and sensitive.They can meet the requirements of food contaminants,especially for rapid detection.They are one of the most popular nanomaterials and have been widely used in the testing of various pollutants in the area of agriculture and food industry.A simple and dual modal?colorimetric and fluorescent?sensor for organophosphate pesticides with high sensitivity and selectivity using adenosine triphosphate?ATP?and rhodamine B-modified gold nanoparticles?RB-AuNPs?,was successfully fabricated.This detection for ethoprophos afforded colorimetric and fluorescence imaging changes visualization.The quantitative determination was linearly proportional to the amounts of ethoprophos in the range of a micromolar scale?4.0–15.0 M?.The limit of detection for ethoprophos was as low as 37.0 nM at 3/k.Moreover,the extent application of this simple assay was successfully demonstrated in tap water samples with high reliability and applicability,indicating remarkable application in real samples.Moreover,based on the suface modification of N₂⁺as a strong stabilizer to gold nano-particles and the electrostatic adherence between the negatively charged fluorescent molecule Cy5.5 and gold nano-particles,we have studied the detection response generated by DTDBD-Cy5.5-AuNPs in different modification states to detect ractopamine,and finally built a dual-channel detection method of high sensitivity and specificity based on DTDBD-Cy5.5-AuNPs to detect ractopamine.Due to the physiological conditions,N₂⁺and phenol react rapidly and produce Azo on the surface of AuNPs,as a consequence,causing the aggregation of nano-gold particles,which can be demonstrated by the optical changes of the AuNPs solution and further be quantified by ultraviolet spectrum.Meanwhile,the release of fluorescent molecules off the surface of gold nano particles causes fluorescence recovery.Therefore,the concentration of ractopamine can be quantitatively determined according to the change of ultraviolet absorption and fluorescence intensity caused by the reaction of DTDBD-Cy5.5-AuNPs colloidal solution and ractopamine.The limit of detection for ractopamine quantified by the colorimetry and fluorescent method are 0.6 nM and1.7nM,respectively.This simple dual-mode assay has been successfully applied in the detection of ractopamine in human urine samples and feeds with high reliability and suitability.