Sensitive Detection Of Chloramphenicol Based On Fluorescence Resonance Energy System By Upconversion Nanoparticles Aptamer Sensor

Chloramphenicol(CAP),a broad-spectrum antibiotic secreted by Streptomyces venezuelae,has been widely used in animal feeding stuff and clinical fields to prevent and treat bacterial diseases as a bacteriostatic drug.The abuse of chloramphenicol will cause it to remain in animal-derived foods.Once it enters the human body,its side effects will threaten physical health,such as aplastic anemia,bone marrow suppression or severely causing cardiovascular failure syndrome.At present,chloramphenicol has been banned in many countries including China,the United States,and the European Union,and it is not allowed to be detected in foods of animal origin.Therefore,it is necessary to develop a simple,effective,highly specific and sensitive method for the detection of chloramphenicol residues in food,which is of great significance for guaranteeing food safety.Upconversion nanoparticles have good photochemical stability,long fluorescence emission lifetime,narrow emission band,large anti-Stokes shift,and under near-infrared light(NIR)excitation.Also,it has a low background value of bioluminescence and high signal-to-noise ratio.Therefore,it is the ideal material to improve the sensitivity of detection.In this study,rare earth-doped upconversion nanoparticles(UCNPs)and gold nanoparticles(AuNPs)were used as donors and acceptors of fluorescent energy,respectively.Based on the fluorescence resonance energy transfer(FRET)system between the two,an aptamer sensor to detect chloramphenicol was established.The specific research contents are as followsFirstly,oleic acid-coated green(NaYF4:Yb,Er)and blue(NaYF4:Yb,Tm)upconversion nanoparticles(UCNPs)were synthesized by solvothermal method.The results show that UCNPs have strong emission at 477 nm and 547 nm under excitation at 980 nm,and the luminescence performance is good.Through TEM characterization,UCNPs are round,uniform particle size and about 40-50 nm and have good dispersion.Then,surface modification of NaYF4:Yb,Er coating the silica shell and amination(UCNPs@SiO2@NH2),the modified material changed from hydrophobic to hydrophilic,which provided favorable conditions for subsequent experimentsSecondly,gold nanoparticles(AuNPs)were prepared by the trisodium citrate reduction method and were characterized by transmission electron microscopy(TEM)and UV-visible spectrophotometry.The results show that the particle size of AuNPs is about 16 nm with a uniform circular shape and good dispersion,and there was an obvious UV absorption peak at 519 nm.Thirdly,an aptamer sensor for detecting chloramphenicol was constructed in a system based on fluorescence resonance energy transfer between upconversion nanoparticles and gold nanoparticles.UCNPs were connected to chloramphenicol aptamers through the streptavidin-biotin amplification system to form fluorescent donor probes(UCNPs-apt),and AuNPs were linked to the sulfhydryl-modified chloramphenicol complementary chains through gold-sulfur bonds to form fluorescent acceptor probes(AuNPs-cDNA).Due to the complementary base pairing of apt and cDNA,the distance between UCNPs-apt and AuNPs-cDNA was narrowed.At this time,the FRET phenomenon resulted in the fluorescence quenching of UCNPs and partial fluorescence recovery after CAP was added Under the optimal detection conditions,the chloramphenicol concentration has a good linear relationship with the fluorescence recovery value.The linear regression equation is y=79.16 lgx+181.57,and R2=0.9988.The detection range was 0.01 ng/mL-10 ng/mL,and the detection limit was 5 pg/mL.This method was used to carry out recovery experiments on milk samples.The recovery rate was 93.5%-99.4%,and the relative standard deviation was 1.18%-2.84%,indicating that the method can be used for the detection of actual samples.