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.