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Click Chemistry Reaction-Triggered 3D DNA Walking Machine for Sensitive Electrochemical Detection of Copper Ion

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journal contribution
posted on 03.09.2018 by Min Qing, Shunbi Xie, Wei Cai, Dianyong Tang, Ying Tang, Jin Zhang, Ruo Yuan
Herein, for the first time, we engineered click chemistry reaction to trigger a 3D DNA walking machine for ultrasensitive electrochemical detection of copper ion (Cu2+), which provided a convenient access to overcome the shortcomings of poor selectivity and limited amplification efficiency in traditional determination of Cu2+. Click chemistry reaction drove azido-S2 to bind with alkynyl-S1 for the formation of a walker probe on aminated magnetic polystyrene microsphere@gold nanoparticles (PSC@Au), which opened the hairpin-locked DNAzyme. In the presence of magnesium ion (Mg2+), the unlocked DNAzyme was activated to cleave the self-strand at the facing ribonucleotide site, accompanied by the release of product DNA (S3) and the walker probe. Therefore, the walker probe was able to open the adjacent hairpin-locked DNAzyme strand and then be released by DNAzyme cleavage along the PSC@Au-DNAzyme track. Eventually, the liberated single-strand S3 induced catalytic hairpin assembly (CHA) recycling, resulting in the capture of a large number of methylene blue-tagged hairpin DNA (MB-H2) on the sensor surface and significant electrochemical responses. By coupling click chemistry reaction with the dual-amplification strategy of the 3D DNA walking machine and CHA recycling, the proposed biosensor not only demonstrated high accuracy and selectivity for Cu2+ detection in real samples but also showed excellent performance for Cu2+ detection with a wide linear range of 1.0 pM to 500 nM and low detection limit of 0.33 pM. Moreover, this elaborated biosensor could be readily expanded to Mg2+ detection with a constant concentration of Cu2+, which paves a new way to apply the 3D DNA walking machine in various ion sensings.