A label-free fluorescent sensing strategy for the rapid and highly sensitive detection of Pb2+ was developed by integrating Pb2+ DNAzyme-specific cleavage activity and a tetrahedral DNA nanostructure (TDN)-enhanced hyperbranched hybridization chain reaction (hHCR). This strategy provides accelerated reaction rates because of the highly effective collision probability and enriched local concentrations from the spatial confinement of the TDN, thus showing a higher detection sensitivity and a more rapid detection process. Moreover, a hairpin probe based on a G-triplex instead of a G-quadruplex or chemical modification makes hybridization chain reaction more controlled and flexible, greatly improving signal amplification capacities and eliminating labeled DNA probes. The enhanced reaction rates and improved signal amplification efficiency endowed the biosensors with high sensitivity and a rapid response. The label-free detection of Pb2+ based on G-triplex combined with thioflavin T can be achieved with a detection limit as low as 1.8 pM in 25 min. The proposed Pb2+-sensing platform was also demonstrated to be applicable for Pb2+ detection in tap water, river water, shrimp, rice, and soil samples, thus showing great potential for food safety and environmental monitoring.

中文翻译：

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基于超支化杂交链式反应驱动的空间定域DNA纳米机器对环境铅离子进行无标记超灵敏检测


通过整合 Pb2+ DNAzyme 特异性裂解活性和四面体 DNA 纳米结构 (TDN) 增强的超支化杂交链式反应 (hHCR)，开发了一种用于快速、高灵敏度检测 Pb2+ 的无标记荧光传感策略。由于高效的碰撞概率和来自 TDN 空间限制的丰富的局部浓度，该策略提供了加速的反应速率，从而表现出更高的检测灵敏度和更快速的检测过程。此外，基于G-三链体而不是G-四链体或化学修饰的发夹探针使杂交链式反应更加可控和灵活，大大提高了信号放大能力并消除了标记的DNA探针。反应速率的提高和信号放大效率的提高赋予生物传感器高灵敏度和快速响应。基于G-triplex结合硫代黄素T的Pb2+无标记检测，25分钟内检测限低至1.8 pM。所提出的 Pb2+ 传感平台还被证明适用于自来水、河水、虾、大米和土壤样品中的 Pb2+ 检测，从而在食品安全和环境监测方面显示出巨大的潜力。