Ultrasensitive Electrochemiluminescence Biosensor for Speedy Detection of microRNA Based on a DNA Rolling Machine and Target Recycling

Intelligent DNA walking machines have become a great hot spot in biosensing, but the walking efficiency of DNA walking machines was still limited due to the low local concentration of substance DNA and the derail of leg DNA. Herein, a Zn2+-driven DNA rolling machine was proposed to overcome the above shortages and applied as a electrochemiluminescence (ECL) biosensor for speedy ultrasensitive detection of microRNA-21. First, the original DNA rolling machine was synthesized by numbers of leg DNA modified on Au nanoparticle which matched with the high concentration of track DNA on the sensing platform and could roll efficiently through Zn2+ driving. By this way the DNA rolling machine not only increased the local concentration of leg DNA and track DNA to improve walking efficiency but also changed the motion mode from step-by-step walking to high-speed rolling, weakening the derailment of leg DNA and shortening the moving time. Second, target-induced recycling and acid dissolution could convert a finite amount of target microRNA into a large amount of Zn2+, which greatly improved the sensitivity of biosensor and overcame the drawbacks of enzyme cleavage or polymerization in common nucleic acid amplification methods. Lastly, the obtained Zn2+ was employed to drive the DNA rolling machine through specific sites recognizing and track DNA cutting to remove a quencher of ferrocene, recovering ECL emission of CdS:Mn QDs for microRNA-21 detection with a detection limit of 0.28 fM. Besides, the biosensor was successfully applied in microRNA-21 analysis from human cancer cell lysates, offered a controllable and ultrasensitive strategy for speedy detection of microRNA, and revealed a new avenue for clinical analyses