Target-switched triplex nanotweezer and synergic fluorophore translocation for highly selective melamine assay
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This paper describes a triplex DNA nanotweezer to specifically capture melamine (MEL). The triplex-forming oligonucleotide (TFO) arm can be switched from the open state to the closed state once MEL binds to the abasic site (AP site) in duplex via the bifacial hydrogen bonding with thymines. Following this nanotweezer operation, the AP site-bound fluorophore is translocated to the terminal triplet to subsequently light up the nanotweezer. The TFO arm is found to be pivotal for permitting the AP site binding. The synergic processes of target competition and fluorophore translocation support a high selectivity for the MEL assay even against the inherent adenosine and the MEL hydrolysis products. Chelerythrine is employed as the fluorescent probe. The detection limit of MEL was estimated to be about 140 nM assuming a signal-to-noise ratio of 3. It was applied to the determination of MEL in spiked milk samples without any separation procedure. Conceivably, this method opens a new avenue towards highly selective triplex-based sensors by making use of other commercially available DNA modifications for recognizing other analytes.
KeywordsDNA Abasic site Switch Fluorescence Fluorometry Chelerythrine Hydrogen bonding Milk
This work was supported by the National Natural Science Foundation of China (Grant No. 21675142) and the National and Zhejiang Undergraduate Training Program for Innovation and Entrepreneurship (Grant No. 201810345017, 201610345011 and 2016R404008).
Compliance with ethical standards
The author(s) declare that they have no competing interests.