A "turn-off" ultra-sensitive fluorescent quantitative biosensor driven by zinc ion DNAzyme.

Highlights • The detection system was driven by Zn2+-dependent Cleavage DNAzyme (17E). • A "turn-off"fluorescent quantitative biosensor based on the cleaved substrate chains unsuitable for RT-qPCR. • This detection system is ultra-sensitive with the minimum limit of 58.61 pM. • In this study, the most active cDNAzyme was selected. • No largE–Scale instruments were needed during the entire detection process. Abstract Although it is normal for trace elements of zinc (Zn2+) to be present in the human body, the lack or excess thereof will affect general human health. Due to the low content of Zn2+ found in the environment, detection technology possessing enhanced sensitivity capabilities is necessary for its identification. For the purpose of this study, a "turn-off" ultra-sensitive fluorescent quantitative biosensor was established, based on Zn2+-dependent Cleavage DNAzyme for the sensitive and specific recognition of Zn2+. Furthermore, the original sequence of the substrate chain, as well as the added primer-binding sequences on either side of the substrate chain were examined without destroying the catalytic and cleavage sites of the enzyme. In the presence of Zn2+, the biosensor circulates continuously to promote catalyzation of the substrate chains cleavage by 17E at the proper temperature. The cleaved substrate chains cannot be used as templates for amplification reactions, while the uncleaved substrate chains can be expanded by PCR amplification and synthesized into large amounts of double-stranded DNA to produce a strong fluorescent signal. Consequently, the cutting effect is demonstrated by the change in the Cq value (ΔCq) both before and after the separation process. The larger the ΔCq value, the smaller the remaining substrate chain, and the better the cutting effect. Sensitivity, detection limit, and specificity analysis, indicates that the Zn2+ quantitative detection system established in this paper displays high sensitivity and specificity. The minimum limit of detection (LOD) can reach at 58.61 pM, which dramatically improves the sensitivity of Zn2+ detection. In conclusion, a simple, rapid, accurate quantitative detection system for Zn2+ was established with both high sensitivity and specificity. [ABSTRACT FROM AUTHOR]