College of Pharmacy, Guangdong Medical University, Dongguan 523000, P. R. China.
Analyst. 2020 Jul 7;145(13):4664-4670. doi: 10.1039/d0an00675k. Epub 2020 May 27.
The efficient detection of illicit drugs such as cocaine continues to be important for the fight against drug trafficking. Herein, we report a one-step method for rapid and specific cocaine detection. The method is based on our finding that small-molecule Thioflavin T (ThT) can act as a fluorescence indicator, which can be bonded with the anti-cocaine aptamer (MNS-4.1) to generate an enhanced fluorescence signal. More interestingly, upon cocaine binding, the intercalated ThT can be replaced, causing a drastic fluorescence reduction. We further optimized the sequence of MNS-4.1 and a new anti-cocaine aptamer (coc.ap2-GC) was obtained. This aptamer showed a higher affinity to both ligands, which increased the ThT binding fluorescence intensity and showed the highest quenching efficiency. Based on the fluorescence change induced by competitive binding, cocaine detection could be accomplished by a "mix-and-detect" strategy within seconds. Such a label-free method exhibits high sensitivity to cocaine with a low detection limit of 250 nM. Moreover, the practical sample analysis (2.5% human urine and saliva) also exhibits good precision and high sensitivity.
快速、特异性检测可卡因等非法药物对于打击毒品走私仍然至关重要。在此，我们报告了一种一步法快速可卡因检测方法。该方法基于我们的发现，小分子硫黄素 T（ThT）可以作为荧光指示剂，与可卡因适体（MNS-4.1）结合产生增强的荧光信号。更有趣的是，可卡因结合后，嵌入的 ThT 可以被取代，导致荧光急剧降低。我们进一步优化了 MNS-4.1 的序列，得到了一种新的可卡因适体（coc.ap2-GC）。该适体对两种配体均显示出更高的亲和力，增加了 ThT 结合荧光强度，并显示出最高的猝灭效率。基于竞争结合诱导的荧光变化，可以通过“混合检测”策略在几秒钟内完成可卡因检测。这种无标记方法对可卡因具有高灵敏度，检测限低至 250 nM。此外，对实际样品（2.5%人尿和唾液）的分析也表现出良好的精密度和高灵敏度。
