| In recent years,the emergence of food safety issues has increasingly attracted the attention of the society.Milk and dairy products as a large category of animal sources(milk,meat,etc.),their safety issues are more extensive.Among them,the problem of antibiotic residue is the most important portion.However,with the rapid development of the milk and dairy industry,antibiotics such as tetracyclines,?-lactams,and aminoglycosides have been widely used in animal husbandry.However,with the rapid development of the milk and dairy industry,antibiotics such as tetracyclines,?-lactams,and aminoglycosides have been widely used in animal husbandry.The fundamental purpose is to protect the health of animals and the economic benefits of animal husbandry.But it also inevitably caused the residue of antibiotics in milk and dairy products.Therefore,in order to solve the problem of antibiotic residues in the dairy industry,the current priority for food safety testing is how to quickly and concisely detect antibiotic residues in milk and dairy products.Liver diseases are getting younger and younger,and there are more and more patients with liver diseases.Liver diseases have received widespread attention from the medical profession.Studies have shown that determining the content of bile acids in patients'serum and urine is a key indicator for checking the liver synthesis,secretion,metabolism and liver damage in patients,and has very important practical significance for medical workers to understand,diagnose and treat liver diseases.Therefore,this study established a method based on aptamer-modified shell isolation nanoparticle-enhanced fluorescence(SHINEF),which achieves highly sensitive and specific fluorescence detection of tetracycline(Tc)and cholic acid(CA).And reached the application in actual samples.(1)An aptamer-labelled flfluorescent nanoprobe-integrated shell-isolated nanoparticle-enhanced fluorescence spectroscopy(SHINEFs)had been proposed for selective and sensitive detection of Tc.In the study,Cd Te quantum dots were used as a flfluorescent source,silica-coated silver nanoparticles(Ag@Si O2)were used as the SHINEFs material for signal amplifification.The maximum SHINEFs was obtained with a 9 nm silica spacer,and optimized the best detection conditions for normal temperature,p H=7 and incubation time of 30 minutes.The linear range of the nanoprobe was from 0.2 to 400?M,and the detection limit was 16.2 n M.Furthermore,our synthesized nanoprobe was applied to detect Tc in milk with a recovery rate of96.50-101.80%.These results showed that the as-prepared nanoprobe was a rapid detection tool for Tc with high sensitivity and selectivity.The aptamer-modifified nanoprobe can also be applied to the analysis of other substances by altering the aptamer.(2)Cholic acid(CA)as an important gut bacterial metabolite in humans would cause DNA damage when its level increases.Determination of CA is extremely significant and necessary in human because of its important in medical and clinical diagnose.Herein,an aptamer modified fluorescent sensor combined surface plasmon resonance(SPR)enhanced fluorescence for signal amplification detection of CA was developed.Silica-coated silver nanoparticles(Ag@Si O2)as SPR materials were decorated with Cd Te quantum dots(QDs)as fluorescent substances.Then CA aptamer was modified to the surface of the Cd Te QDs(Ag@Si O2@QDs-Apt)through the covalent binding for specific recognition of CA.The maximum fluorescent enhancement was obtained with 33 nm of Ag nanoparticle,and optimized the best detection conditions for normal temperature,p H=7 and incubation time of 30 minutes.Compared with aptamer-modified QDs(QDs-Apt),Ag@Si O2@QDs-Apt showed super sensitivity with the linear range of 0.1-500?M.In order to verify the application,the developed nanosensor was applied to the detection of CA in human serum and urine with the recovery rate of 95.8-110.4%.(3)In addition to the methods we have established for the detection of tetracycline antibiotics,we have selected three commonly used detection methods to compare with our detection methods,including microbial antibacterial method,high performance liquid chromatography and liquid mass spectrometry.Among them,the microbial antibacterial method used Bacillus subtilis and Escherichia coli as the test bacteria for in vitro antibacterial activity determination,and the results showed that tetracycline has a certain antibacterial effect on the two test bacteria.In the high performance liquid chromatography experiment,acetonitrile was used to precipitate the protein and then centrifuged,and the HPLC was equipped with a UV detector for determination.The results show that:the recovery rate of the sample addition is84.55%-121.40%,and the relative standard deviation is between 1.22%-7.23%.The experimental results of LC/MS are as follows:the sample recovery rate is80.00%-137.00%,and the relative standard deviation is between 2.80%-15.00%.Through comparison,it can be found that the fluorescence quantum dot detection method established in this study is simple and easy to operate.The time-consuming is short and the detection limit is low,and it has a good application prospect. |
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