Application Of Aptamer-functionalized Gold And Silver Nanomaterials In The Colorimetric Detection Of Tetracycline

Tetracycline（TET）is a common antibiotic widely used to treat bacterial infections and to promote animal growth.However,the residue of TET also threatens human health,and will cause adverse consequences such as drug-resistant strains and tetracycline teeth.Strictly controlling the residues of TET is of great significance to the healthy life of human beings.It is of great practical significance to develop a sensitive,efficient and simple TET residue detection and analysis method.In this paper,by taking advantage of the advantages of high specificity,high sensitivity and low cost of aptamers（Apt）,as well as the excellent optical properties and catalytic properties of noble metal nanoparticles,a series of colorimetric aptamers-precious metal nanoparticles-based TET were developed.Detection method.The research content includes the following aspects:（1）TET residues exist in our lives and endanger our health.To rapidly detect TET,we designed a colorimetric aptasensor for TET based on Apt to control the aggregation of silver nanoparticles（Ag NPs）.Apt was adsorbed on the surface of Ag NPs to protect the Ag NPs from salt-induced aggregation and maintain a dispersed state.The color of the solution was bright yellow.In the presence of TET,Apt was desorbed from the surface of Ag NPs and highly bound to TET to form a rigid structural complex.Ag NPs without Apt protection aggregated under the induction of salt,and the solution color changed to pink.By comparing the effects of three Apts with different chain lengths on the determination of TET,we found that the shortest Apt was the best for stabilizing Ag NPs.The colorimetric aptasensor constructed based on this mechanism is not only sensitive and fast,but also exhibits high specificity even in the presence of TET analogs,such as chlortetracycline（CTC）and oxytetracycline（OTC）.The linear range of the method under the optimal experimental conditions was 40 to 480 n M,and the detection limit（LOD）was 4.33n M.The method was used for TET detection in milk samples with recoveries ranging from 95.14%to 107.26%,and with relative standard deviations（RSDs）ranging from1.57%to 4.95%.The potential of the colorimetric aptasensor in food safety detection is demonstrated.（2）Based on the dual regulation of aggregation of gold nanoparticles（Au NPs）and in situ silver metallization,a colorimetric aptasensor for the determination of tetracycline antibiotics（TCs）in complex matrices was constructed.Aptamer-functionalized Au NPs can catalyze the reaction between p-aminophenol and silver ions（Ag⁺）and promote the in situ deposition of Ag shell on Au NPs,resulting in the formation of gold-silver core-shell bimetallic nanoparticles（Au@Ag NPs）.When the target is present,Apt detaches from the Au NPs surface due to the aptamer-target interaction.With the desorption of Apt,the Au NPs catalyzed the further aggregation of Au@Ag NPs,and the resulting Ag shell became thinner,corresponding to the gradual change of solution color from orange-yellow to brown.Using A₆₀₀/A₄₁₀as the measurement signal,the TCs showed an obvious linear relationship in the range of0.3～6.0μM,and the LOD was 33.6 n M.In particular,the method was successfully applied to detect TCs in honey samples and human urine samples with recoveries ranging from 91.2%to 106%with RSDs less than 4.6%.These results meet the requirements of actual sample analysis.（3）We propose a method for the reduction of aniline to polyaniline using aptamer-functionalized Au NPs.Based on the specific binding ability of the Apt to the target,we found that the rigid structure complex of aptamer-tetracycline has an inhibitory effect on the formation of polyaniline.Based on this,a colorimetric aptasensor for detecting TCs was established.In the absence of TCs,Au NPs catalyzed aniline to blue polyaniline under acidic conditions.In the presence of TCs,the formation of aptamer-tetracycline complexes hindered the formation of polyaniline,causing the solution color to gradually change from blue to pink.Under the optimal experimental conditions,using A₇₀₅/A₅₃₀as the detection signal,the measured TCs showed a good linear relationship in the range of 0.3～6.0μM,and the LOD was 5.01 n M.The method was successfully applied to the detection of TCs in honey samples,with recoveries ranging from 92.1 to 102.3%and RSDs less than4.46%.