Development Of Optical Sensors Based On Aptamer Recognition For The Detection Of Tetracycline In Food

Tetracycline（TC）has been widely used to control and prevent animal diseases due to its broad-spectrum antibacterial properties and low cost.However,tetracycline residues have also become one of the hidden dangers of food safety.It is of great significance to establish a simple,rapid and sensitive method for the detection of antibiotics in food.Immunoassay based on antigen-antibody recognition is the main method for rapid detection of tetracycline,but antibody has the disadvantages of high price and poor stability.In recent years,aptamers have been widely used in analytical sensing field due to their high efficiency,stability and low price.In this study,two indirect competitive enzyme linked aptamer optical sensors were developed based on aptamer recognition principle,which have three signal outputs of colorimetric/fluorescence/scattering,and have been successfully applied to the detection of tetracycline residues in milk,honey and other foods.The main research contents are as follows:（1）Based on recognition and enzyme mediated adapter body growth of silver nanoparticles optical signal sensor detection of tetracycline,with fit body as original identification of tetracycline,fit body tag in the MPP tetracycline（TC-BSA）and tetracycline competition recognition under test,and through the avidin biotin-specific role will fit on the body tag alkaline phosphatase（ALP）.Subsequently,enzyme substrate ascorbate phosphate（AAP）was added,and ALP was used to catalyze AAP to produce reducing substance ascorbic acid（AA）,which was then mixed with detection solution containing silver ions,sodium hydroxide and 2-amino terephthalic acid,a fluorescent signal molecule.AA reduces silver ions to produce silver nanoparticles（Ag NPs）,which causes the solution to change from colorless to yellow,and the fluorescence and scattering light are weakened,that is,it has three signal output.The concentration of tetracycline in the samples to be tested is proportional to the amount of Ag NPs generation,thus achieving the quantitative detection of tetracycline.The detection limits of tetracycline were 1.67×10^-2 ng/m L for colorimetric method,5.3×10^-3 ng/m L for fluorescence method and 1.02×10^-2 ng/m L for scattered light method,respectively.The sensor has good reliability when used to detect tetracycline residues in milk and honey.（2）Tetracycline detection by multi-optical signal sensor based on aptamer recognition and enzyme mediated etching of Silver nanocrystalline@carbon dot:Synthesis of Silver nanoparticle carbon dot composite（Ag NPs@CDs）;The aptamer was used as the recognition element of tetracycline.The aptamer competed for the recognition of TC-BSA and tetracycline in the microporous plate,and labeled ALP by avidin-biotin specific effect.Through the catalysis of ALP to AAP,reducing substance AA is produced.Hydrogen peroxide（H₂O₂）can etch Ag NPs@CDs and cause changes of color,fluorescence and scattered light.AA can redox with H₂O₂ to inhibit the etching of Ag NPs@CDs.The concentration of tetracycline in the tested samples is inversely proportional to the etch degree of Ag NPs@CDs,thus achieving the quantitative detection of tetracycline.The detection limits of tetracycline were 7.9×10^-3 ng/m L for colorimetric method,1.7×10^-2 ng/m L for fluorescence method and 1.6×10^-2 ng/m L for scattered light method,respectively.The sensor has good reliability when used to detect tetracycline residues in milk and honey.