Study On The Detection Methods Of AFB1 Based On Core-shell Upconversion Fluorescent Nanoparticles

With the improvement of living standards,food safety issues have attracted people’s attention gradually.Among them,aflatoxin B1(AFB1)in food and agricultural products like peanuts,milk,feed,and grain has a very high carcinogenicity.Even at a low concentration,it can cause food contamination and liver disease such as cirrhosis and liver cancer.So it is a major threat to human health.Therefore,finding a simple and sensitive AFB1 detection method is of great significance for food safety and human health.Rare earth doped upconversion nanoparticles can absorb near-infrared light and convert it into visible light.They have the advantages of stable fluorescence,antiphotobleaching and long fluorescence lifetime(up to several tens of milliseconds).As a result,they have important potential.in the field of analysis and detection.In this paper,rare earth doped upconversion nanoparticles were prepared by high-temperature solvothermal method,and the shells were coated by layer-by-layer method to improve the fluorescence intensity.The AFB 1 aptamer was used to couple with core-shell upconversion nanoparticles to establish a fluorescent nanoprobe.Based on this,we have established two methods for detecting AFB1 by combining immunochromatographic technology and the principle of fluorescence resonance energy transfer.The main work is as follows:The first method is to develop an upconversion fluorescence-aptamer immunochromatographic test strip to detect AFB 1.Firstly,we used ligand exchange to modify the upconversion nanoparticles and couple them to AFB1 aptamers to construct upconversion fluorescent nanoprobes.Then we combine with immunochromatographic test strips and small molecule competition method for rapid trace detection of AFB 1.The result shows a good linear relationship when the concentration of AFB 1 ranges from 5 to 100 ng/mL,and the detection limit is 2.4 ng/mL.The second method is based on the principle of fluorescence resonance energy transfer to construct an upconversion fluorescence-aptamer sensor to detect AFB1.In this method,AFB1 aptamer is connected to upconversion nanoparticle to act as an energy donor.Another oligonucleotide that modifies with the quenching group BHQ1 is used as an energy acceptor.The two are combined through the principle of complementary base pairing,thereby increasing the distance between upconversion nanoparticle and the quenching group BHQ1.As a result,the fluorescence resonance energy transfer occurs and the upconversion fluorescence is quenched.When AFB1 is existed,AFB1 will bind to its aptamer specifically,resulting in dissociation of the double-strand and upconversion fluorescence recovery.Quantitative detection of AFB1 by measuring the fluorescence intensity at 546 nm of upconversion nanoparticles shows a good linear relationship when the concentration of AFB1 at 5-200 ng/mL,and the detection limit is 0.2376 ng/mL.