基于核酸适配体杂交链式反应比色法检测鼠伤寒沙门氏菌

该研究探讨了基于核酸适配体特异性识别机制和杂交链式反应（hybridization chain reaction，HCR）扩增策略，以金纳米粒子（gold nanoparticles，AuNPs）颜色变化为比色信号，设计了一种无标记、无酶、灵敏的鼠伤寒沙门氏菌（Salmonella typhimurium，S. typhimurium）比色检测法。根据鼠伤寒沙门氏菌核酸适配体设计引发链和两个发夹探针，核酸适配体捕获鼠伤寒沙门氏菌，触发引发链打开发夹探针，发生杂交链式反应，在实现目标菌信号放大同时，利用反应前发夹探针粘性末端以及反应后形成的杂交长链对金纳米粒子结合差异性，产生比色信号，实现鼠伤寒沙门氏菌的快速检测。通过对杂交链式反应时间、发夹探针与金纳米粒子结合时间以及发夹探针浓度等实验参数进行优化，提高实验灵敏度。在最优实验条件下，鼠伤寒沙门氏菌浓度对数值与紫外吸光比值（A630/525）在103~107 CFU/mL范围内呈现良好的线性关系，检测限为6.3×101 CFU/mL，在牛奶样品中加标回收率为90.05%~109.97%。本比色法操作方便，无需要化学修饰以及复杂仪器且实验结果可视，为鼠伤寒沙门氏菌监测提供一种新的方法。

Colorimetric Detection of Salmonella typhimurium Based on Hybridization Chain Reactions and Aptamer

A label-free, enzyme-free, and sensitive colorimetric detection method of Salmonella typhimurium (S. typhimurium) detection was proposed based on the recognition mechanism of the aptamer and the amplification strategy of hybridization chain reactions (HCRs) using the color variations of gold nanoparticles (AuNPs) as the colorimetric signals. An initiator and two hairpin probes in the HCR system were designed based on the aptamer of S. typhimurium. The aptamer binds to S. typhimurium DNA, thereby triggering the initiator to open the hairpin probes. This way, HCRs are initiated. While achieving the signal amplification for the target bacteria, the differences in the binding of the sticky ends of the hairpin probes before the reaction and the hybrid long chain formed after the reaction with gold nanoparticles was used to obtain the colorimetric signals, which results in rapid detection of S. typhimurium. Experimental parameters, such as the hybridization chain reaction time, binding time of the hairpin probes with gold nanoparticles, and concentrations of hairpin probes, have been optimized to improve the detection sensitivity. Under the optimal conditions, the logarithmic value of the S. typhimurium concentration and UV absorbance ratio (A630/525) exhibited a good linear relationship in the range of 103~107 CFU/mL. The detection limit equals 6.3×101 CFU/mL, and the spike recovery rate for milk samples ranges between 90.05%~109.97%. The proposed colorimetric method is easy and simple, and it does not require any chemical modification and complicated equipment. Furthermore, the experimental results are visible. This research provides a new method for rapid detection of S. typhimurium.