用于检测水环境中银离子浓度的荧光适体传感器研究

银凭借其独特的性能，在医疗材料、摄影、电子、成像等行业中应用广泛。然而，银离子被列为最具毒性的重金属离子之一，会对环境以及人类的生命健康造成严重威胁。为了灵敏、特异性的检测水环境中的银离子浓度，利用纳米金的优良光学猝灭性以及双链核酸适体捕获银离子能力更强的优点，结合荧光能量共振转移原理，提出一种用于检测水环境中银离子浓度的荧光适体传感器。将修饰SH键的核酸适体与纳米金混合形成稳定的纳米结构，并加入标记有FAM的核酸适体，形成检测银离子浓度的工作溶液。当不存在银离子时由于不匹配碱基C-C之间的排斥力导致两条核酸适体不结合，反应体系中具有较强的荧光；当存在银离子时，双链核酸适体中不匹配的C-C能与银离子通过金属离子-碱基的相互作用形成稳定的C-Ag+-C碱基对，这种复合结构的产生会拉近纳米金和荧光基团之间的距离，使得荧光信号随着银离子浓度的增加而逐渐减弱。根据加入银离子前后荧光强度的变化可实现银离子浓度的检测。同时，为了提高传感器的灵敏性和稳定性，实验优化了工作溶液中纳米金与核酸适体的浓度比、氯化钠浓度、缓冲液的pH以及培养温度等参数。结果表明，当浓度为0.012 5 g·L-1的纳米金与5 μmol·L-1核酸适体的体积比为5∶1，NaCl浓度为260 mmol·L-1，缓冲液pH 7，培养温度为30 ℃时，工作溶液初始荧光强度最强，银离子检出限为10 nmol·L-1，相关系数为R2=0.99。此外，该传感器对银离子的浓度检测表现出较好的特异性，且具有操作简单、灵敏和不引入有毒溶剂等优点，在水环境中的银离子浓度检测领域有较好的应用前景。

A Fluorescence Aptasensor for Detecting Silver Ion Concentration inAqueous Environment

Silver is widely used in medical materials,photography,electronics,imaging and other industries because of its unique properties.However,silver ions are listed as one of the most toxic heavy metal ions,which poses a serious threat to the environment and human health.In order to detect the concentration of silver ions in an aqueous environment sensitively and accurately,a fluorescence aptasensor for detecting the concentration of silver ions in aqueous environment is proposed,which takes advantage of the excellent optical quenching property of nanogold and the stronger ability of double chain aptamers to capture silver ions based on the principle of fluorescence energy resonance transfer.Aptamer modified with SH bonds were mixed with nanogold to form stable nanostructures,and aptamer labeled with FAM were added to form a working solution to detect the concentration of silver ions.In the absence of silvers,two aptamers cannot hybridize with each other due to the repulsive force between the mismatched bases C—C,and the reaction system has strong fluorescence.In the presence of silver ions,the mismatched C—C in the double-stranded aptamers can form a stable C—Ag⁺—C base pair with the silver ions through the interaction between metal ion and base.The generation of this composite structure will shorten the distance between the gold nanoparticles and the fluorophore,so that the fluorescence signal will gradually weaken with the increase of silver ion concentration.According to the change of fluorescence intensity before and after adding silver ion,the concentration of silver ion can be detected.At the same time,in order to improve the sensitivity and stability of the sensor,the concentration ratio of gold and nucleic acid aptamers in the working solution,the concentration of sodium chloride,the pH of the buffer and the culture temperature were optimized.The results showed that when the volume ratio of 0.0125 g·L^-1nano gold to 5μmol·L^-1aptamer was 5∶1,the concentration of NaCl was 260 mmol·L^-1,the pH of the buffer was 7,and the culture temperature was 30℃,the initial fluorescence intensity of the working solution was the strongest,the detection limit of silver ion was 10 nmol·L^-1,and the correlation coefficient was R^( 2)=0.99.Based on the characteristics of high recognition ability and strong affinity of aptamers to silver ions,the sensor showed good selectivity to silver ions and was not disturbed by other substances.In addition,the sensor has good specificity for silver ion concentration detection,and has the advantages of simple operation,sensitivity and no introduction of toxic solvents,so it has a good application prospect for silver ion concentration detection in the water environment.