Lu Liling, Han Xiao, Lin Jingwen, Zhang Yingxin, Qiu Minghao, Chen Ying, Li Meijin, Tang Dianping
Key Laboratory for Analytical Science of Food Safety and Biology (MOE & Fujian Province), State Key Laboratory of Photocatalysis on Energy and Environment, Department of Chemistry, Fuzhou University, Fuzhou 350116, P. R. China.
Analyst. 2021 Apr 26;146(8):2664-2669. doi: 10.1039/d1an00178g.
Herein a rapid and sensitive fluorometric bioanalysis platform for mercury(ii) (Hg2+) detection was innovatively developed using ultrathin two-dimensional MXenes (Ti3C2) as fluorescence quencher and Hg2+-induced exonuclease III (Exo III)-assisted target recycling strategy for efficient signal amplification. Initially, fluorophore-labeled single-stranded DNA (FAM-labeled probe) can be easily adsorbed onto the surface of ultrathin Ti3C2 nanosheets by hydrogen bonding and metal chelating interaction, and the fluorescence signal emitted by the FAM-labeled probe is quenched strongly owing to the fluorescence resonance energy transfer between the FAM and ultrathin Ti3C2 nanosheets. Upon sensing the target Hg2+, the protruding DNA fragment at the 3' end of hairpin will hybridize with primer (hairpin-Hg2+-primer), and then further digested by Exo III to produce a probe (nicker). The released target Hg2+ and primer continue to participate in the next recycling, resulting in more hairpin probes becoming nickers. The combination of a large number of nickers and FAM-probe resulted in a significant increase in the fluorescence signal of the system, which was attributed to the fact that the double helix DNA was more rigid and separated from the surface of the ultrathin Ti3C2 nanosheets. The obvious fluorescence signal change of the Ti3C2-based Exo III-assisted target recycling can be accurately monitored by fluorescence spectrometry, which is also proportional to the concentration of Hg2+. Under optimum operating conditions, the peak intensity (520 nm wavelength) of fluorescence increased with increasing Hg2+ within a wide dynamic working range from 0.05 nM to 50 nM (R2 = 0.9913) with a limit of detection down to 42.5 pM. The proposed strategy uses ultrathin MXenes as a platform for binding nucleic acids, which contributes to its potential in nucleic acid hybridization-based biosensing and/or nucleic acid signal amplification bio-applications.
在此，创新性地开发了一种用于汞（II）（Hg2+）检测的快速灵敏的荧光生物分析平台，该平台使用超薄二维MXenes（Ti3C2）作为荧光猝灭剂，并采用Hg2+诱导的核酸外切酶III（Exo III）辅助的靶标循环策略进行高效信号放大。最初，荧光团标记的单链DNA（FAM标记的探针）可以通过氢键和金属螯合相互作用轻松吸附到超薄Ti3C2纳米片的表面，并且由于FAM与超薄Ti3C2纳米片之间的荧光共振能量转移，FAM标记的探针发出的荧光信号被强烈猝灭。在检测到目标Hg2+时，发夹结构3'端突出的DNA片段将与引物杂交（发夹-Hg2+-引物），然后进一步被Exo III消化产生探针（切口）。释放的目标Hg2+和引物继续参与下一轮循环，导致更多的发夹探针变成切口。大量切口与FAM-探针的结合导致系统荧光信号显著增加，这归因于双螺旋DNA更刚性并与超薄Ti3C2纳米片表面分离。基于Ti3C2的Exo III辅助靶标循环的明显荧光信号变化可以通过荧光光谱法准确监测，其也与Hg2+的浓度成正比。在最佳操作条件下，荧光峰强度（520 nm波长）在0.05 nM至50 nM的宽动态工作范围内随Hg2+浓度增加而增加（R2 = 0.9913），检测限低至42.5 pM。所提出的策略使用超薄MXenes作为结合核酸的平台，这有助于其在基于核酸杂交的生物传感和/或核酸信号放大生物应用中的潜力。
