Nanosensor Based on the Dual-Entropy-Driven Modulation Strategy for Intracellular Detection of MicroRNA

The entropy-driven strategy has been proposed as a milestone work in the development of nucleic acid amplification technology. With the characteristics of an enzyme-free, isothermal, and relatively simple design, it has been widely used in the field of biological analysis. However, it is still a challenge to apply entropy-driven amplification for intracellular target analysis. In this study, a dual-entropy-driven amplification system constructed on the surface of gold nanoparticles (AuNPs) is developed to achieve fluorescence determination and intracellular imaging of microRNA-21 (miRNA-21). The dual-entropy-driven amplification strategy internalizes the fuel chain to avoid the complexity of the extra addition in the traditional entropy-driven amplification strategy. The unique self-locked fuel chain system is established by attaching the three-stranded structure on two groups of AuNPs, where the Cy5 fluorescent label was first quenched by AuNPs. After the target miRNA-21 is identified, the fuel chain will be automatically unlocked, and the cycle reaction will be driven, leading to fluorescence recovery. The self-powered and waste-recycled fuel chain greatly improves the automation and intelligence of the reaction process. Under the optimal conditions, the linear response range of the nanosensor ranges from 5 pM to 25 nM. This nanoreaction system can be used to realize intracellular imaging of miRNA-21, and its good specificity enables it to distinguish tumor cells from healthy cells. The development of the dual-entropy-driven strategy provides an integrated and powerful way for intracellular miRNA analysis and shows great potential in the biomedical field.