荧光银纳米簇免标记分子信标检测DNA序列

Detection of DNA sequence by label free silver nanoclusters molecular beacon

DNA模板序列可以影响银纳米簇荧光强度,在此基础上设计了一种免标记分子信标应用于检测DNA序列.与传统发光基团-淬灭基团型分子信标信号模式相反,当探针成发卡状时由于胞嘧啶的增强效应,体系呈现较强荧光;加入目标DNA之后,发卡状结构被打开,胞嘧啶与银纳米簇模板序列远离,体系荧光强度下降.其荧光强度变化与目标DNA浓度成正比并在10~1 000 nmol·L^(-1)的范围内具有良好的线性关系,检出限为7.6 nmol·L^(-1).

With the development of technology, metal nanoclusters are more and more widely used in biomedical field. Silver nanoclusters have become a research hotspot in recent years due to their excellent physical and chemical properties. With adjustable fluorescence emission by different DNA templates, the multifunctional design and application of silver nanoclusters can be realized. Nucleic acid, as the basic life material, plays an irreplaceable role in life activities, which is related to many diseases as biomarkers. At present, the detection of nucleic acid can effectively assist the judgment of diseases. So, we need more and more accurate and rapid methods to detect nucleic acids.In this study, we successfully construct a label-free, low consumption and facile hairpin probe based on DNA templated silver nanoclusters to detect the concentrations of target DNA. Firstly, we prepared red emitting silver nanoclusters in water. The reasons for red emitting silver nanoclusters are analyzed as follows:(1) Higher concentration of silver ions can form larger size silver nanoclusters, which can promote the formation of red emitting silver nanoclusters;(2) Magnesium ion is introduced into the solution, which can protect the negative charge on the DNA structural framework, leading to the synthesis of silver nanoclusters with emitting red light;(3) Based on the previous experience, the DNA template used for the synthesis of silver nanoclusters is considered to be the template emitting near-infrared light. Secondly, based on the influence of the DNA template sequence on the formation of silver nanoclusters, we designed a label-free molecular beacon to detect DNA sequences. Contrary to the traditional dye and quencher molecular beacon signal mode, the hairpin-like probe exhibits strong fluorescence due to the enhancement effect of the C-rich sequence. We design six similar probes to demonstrate that the strong fluorescence enhancement occurred in the present of both the silver nanoclusters template and C-rich sequence. After adding the target DNA, the hairpin-like structure is opened, the C-rich sequence is far away from the silver nanoclusters template sequence, and the fluorescence of the system decreases. Finally, the change in fluorescence intensity is proportional to the target DNA concentration and has a good linear relationship range from 10 to 1 000 nmol·L^(-1)with detection limit of 7.6 nmol·L^(-1). The selectivity is also studied.The DNA detection method studied in this paper has the advantages of low cost, simple operation, high sensitivity and high selectivity, and it can also avoid the complicated steps of labeling dyes.