Based on the high recognition ability and flexible programmability of GR5 DNAzyme, two fluorescent biosensors were engineered for amplified detection of Pb²⁺ via incorporating Ti₃C₂T_X MXenes and embedding 2-aminopurine (2-AP), respectively. The quencher-required approach relied on the DNA affinity and fluorescence quenching ability of Ti₃C₂T_X MXenes. Benefiting from the low background signal modulated by Ti₃C₂T_X MXenes, the sensitive determination of Pb²⁺ was achieved in the linear range of 0.2–10 ng mL⁻¹ with the limit of detection (LOD) of 0.05 ng mL⁻¹. The quencher-free approach combined the fluorescent trait of 2-AP embedded in DNA structure, and the RNA cleavage-propelled digestion process of Exonuclease I (Exo I) for signal amplification, indicating the sensitive detection of Pb²⁺ with the LOD as low as 0.02 ng mL⁻¹ in the linear range of 0.1–10 ng mL⁻¹. Both DNAzyme assays exhibited simple procedures, favorable specificity, rapid analysis, and satisfactory application in standard reference materials (lead in drinking water) and spiked water samples. The two fluorescent biosensors established in this work would not only provide theoretic fundament for DNA adsorption of Ti₃C₂T_X MXenes and the design of 2-AP-embedded DNAzyme assays, but also hold a great potential for on-site monitoring of lead pollution in water samples.

基于 GR5 DNAzyme 的高识别能力和灵活的可编程性，设计了两种荧光生物传感器，分别通过掺入 Ti ₃ C ₂ T _X MXenes 和嵌入 2-氨基嘌呤 (2-AP)来放大检测 Pb ^{2+ 。}需要淬灭剂的方法依赖于 Ti ₃ C ₂ T _X MXenes 的 DNA 亲和力和荧光淬灭能力。受益于 Ti ₃ C ₂ T _{X MXenes 调制的低背景信号，在 0.2–10 ng mL} ^-1的线性范围内实现了Pb ²⁺的灵敏测定检测限 (LOD) 为 0.05 ng mL ^-1。无猝灭剂的方法结合了嵌入 DNA 结构中的 2-AP 的荧光特性，以及用于信号放大的核酸外切酶 I (Exo I) 的 RNA 切割推动的消化过程，表明 Pb ²⁺的灵敏检测与 LOD 低在 0.1-10 ng mL ^-1的线性范围内为 0.02 ng mL ^-1。两种 DNAzyme 测定都表现出简单的程序、良好的特异性、快速分析以及在标准参考物质（饮用水中的铅）和加标水样品中的令人满意的应用。本工作建立的两种荧光生物传感器不仅为 Ti ₃ C ₂ T的 DNA 吸附提供了理论基础。_X MXenes 和嵌入 2-AP 的 DNAzyme 分析的设计，在现场监测水样中的铅污染方面也具有巨大潜力。