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DNA-templated copper nanoclusters obtained via TdT isothermal nucleic acid amplification for mercury(ii) assay

He, Jing-Lin, Wang, Xing-Xing, Mei, Ting-Ting, Wu, Ling, Zeng, Ju-Lan, Wang, Jian-Hui, Wang, Jianxiu, Yu, Donghong, Cao, Zhong
Analytical methods 2019 v.11 no.32 pp. 4165-4172
analytical methods, chemical species, copper, copper nanoparticles, fluorescence, gene amplification, mercury, nucleotidyltransferases, toxicity, washing, water quality
Herein, DNA-templated copper nanoclusters (CuNCs) synthesized by terminal deoxynucleotidyl transferase (TdT) isothermal nucleic acid amplification (INAA) were proposed for Hg²⁺ assay. TdT recognized the 3′-OH end of primers and subsequently prolonged the single strand poly-T at 3′-OH with the assistance of deoxythymidine triphosphate (dTTP). The generated products coordinated with the copper ions to form DNA-templated CuNCs, resulting in remarkable fluorescence. The introduction of Hg²⁺ made the primers form a T–Hg²⁺–T mismatch duplex, which prevented the capture of the 3′-OH end by TdT. The poly-T single strand prolongation reaction was suspended; this led to fluorescence quenching. Hg²⁺ could be detected at a concentration as low as 76 pM with a significant linear range from 0.2 to 500 nM. This method, performed in one tube in one step, does not involve washing and separation steps, which provides a novel insight into the ultra-sensitive detection of toxic analytes in water quality applications.