Target-responsive dumbbell probe-mediated rolling circle amplification strategy for highly sensitive Hg2+ detection?

RSC Advances Pub Date: 2014-05-16 DOI: 10.1039/C4RA02266A

Abstract

A novel label-free amplified fluorescent sensing scheme based on target-responsive dumbbell probe-mediated rolling circle amplification (D-RCA) has been developed for sensitive and selective detection of mercuric ions. In this strategy, we reported an ingeniously designed dumbbell-shaped DNA probe (D-DNA) that integrates target-binding, amplification and signaling within one multifunctional design. An Hg2+–primer DNA (Hg2+–p-DNA) was designed to be complementary to the region of D-DNA but with T–T mismatches. The mismatched Hg2+–primer cannot initiate the RCA reaction in the absence of Hg2+. Stable T–Hg2+–T can be formed in the presence of target Hg2+, thus it induces the elongation and amplification reaction by a RCA mechanism, resulting in numerous cascade dumbbell probes forming duplex G-rich quadruplex oligomeric structures . Upon addition of N-methyl mesoporphyrin IX (NMM), the signal reporter, a strong interaction between the G-quadruplex and NMM brings about a great fluorescence enhancement. In this way, we successfully converted each Hg2+-triggered D-RCA reaction event into detectable fluorescent signals, which were significantly amplified by RCA in an isothermal fashion. This approach can detect 80 fM of mercuric ions, much lower levels than previously reported biosensors, and exhibits high discrimination ability. More significantly, the dynamic range of D-RCA is extremely large, covering 5 orders of magnitude. We also demonstrate Hg2+ quantification with this highly sensitive and selective D-RCA strategy in real samples.

Graphical abstract: Target-responsive dumbbell probe-mediated rolling circle amplification strategy for highly sensitive Hg2+ detection
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