A novel method based on the separation and enrichment effect of magnetic beads and the fully complementary hybridization of two DNA strands was developed for highly sensitive detection of bacterial DNA using a surface-enhanced Raman spectroscopy (SERS) with 5,5’-dithio-bis(2-nitrobenzoic acid) (DTNB)-modified gold nanoparticles as reporter probes. Capture probe was immobilized onto the surface of streptavidin-enwrapped magnetic beads ( SA-MB ) through high affinity between biotin and avidin, by which the target bacterial DNA sequences that connected with the reported probe decorated AuNPs with DTNB and SH-DNA ( AuNPs@DTNB@DNA) were captured and loaded onto the magnetic beads by the hybridization reaction with the capture probe. Compared with previous methods, this design shortened the distance between particles by the ways that the magnetic beads tempted to nanoparticles aggregation, and produced the plasma resonance coupling effect, which increased the SERS signal significantly. The results showed that, under the optimized conditions and in the concentration range from 5 pmol/L to 5 nmol/L, the method performed a good linear relationship between Raman intensity and DNA concentration. The limit of detection ( LOD) of bacterial DNA was estimated to be 5 pmol/L. The method is simple and low cost, and can be used in the sensitive and selective detection of bacterial DNA.%以5,5'-二巯基-双(2-硝基苯甲酸)(DTNB)为拉曼标记分子,利用磁珠的分选富集作用以及完全互补的两条DNA链间的杂交作用力,构建了一种基于表面增强拉曼技术检测细菌DNA的超灵敏方法。链霉亲和素包裹的磁珠通过生物素-亲和素连接上捕获探针,与目标细菌DNA序列部分互补杂交,目标链的另一端与拉曼染料和纳米金功能化的报告探针DNA链互补杂交。此设计利用磁球的聚集作用诱使颗粒间距离缩短,产生了等离子体共振耦合效应,从而使得检测的SERS信号显著增强。结果表明,在优化条件下,DNA浓度在5 pmol/L~5 nmol/L范围内,拉曼强度与DNA浓度的对数呈现较好的线性关系,检出限约为5 pmol/L。该方法设计简单,花费低廉,能用于细菌DNA灵敏且有选择性的检测。
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