NIR-photoactivatable DNA nanomachines for spatiotemporally controllable monitoring of microRNA-21 in living cells based on signal amplification strategy

Precise and spatiotemporally controllable analysis of microRNA-21 in living cells is crucial for accurate diagnosis and effective treatment of related diseases. Herein, a near-infrared (NIR)-photoactivatable DNA nanomachine (PUCNPs-NH2/PEG-ZL-DNA) was constructed for the precise analysis and diagnosis of microRNA-21 in tumor cells. Peanut-shaped upconversion nanoparticles (PUCNPs) were employed as the carriers and activators for the intelligent DNA probe, specifically enabling the cleavage of the photocleavable linker (PC-linker) from the hairpin DNA probe (Hp-Dzy) upon exposure to 808 nm irradiation. In the presence of the target microRNA-21, the locker DNA hybridized with microRNA-21 and the DNAzymes was freed to hybridize with the looped portion of the hairpin DNA (Hp-1). Mg2+ was employed as the cofactor, facilitating the precise cleavage of Hp-1, which triggered the restoration of fluorescence signals. Subsequently, DNAzymes exhibited the competency to selectively recognize and engage with additional Hp-1, and the fluorescence signals were effectively amplified by the recycling process. Consequently, the DNA nanomachine exhibited a linear response to microRNA-21 concentrations ranging from 0.5 nM to 1.0 mu M, achieving a remarkable detection limit (LOD) of 1.19 nM under the optimal conditions. This strategy is realized through the integration of photocontrollable upconversion nanotechnology with the signal amplification approach, showing feasible prospects for spatiotemporally precise and highly sensitive monitoring of microRNA in tumor cells.