Mature microRNAs (miRNAs) are closely associated with cell proliferation and differentiation, stress response, and carcinogenesis, and monitoring intracellular miRNAs can contribute to the studies of their regulatory roles and molecular mechanisms of disease progression. However, accurate and reliable detection of mature miRNAs in complex physiological environments encounters the challenge of undesired detection accuracy ascribed to the coexistence of their precursor microRNAs (pre-miRNAs) and degradation of sensing probes. Here, we demonstrate the synthesis of a new size-discriminative DNA nanocage framework (DNF) for the sensitive monitoring of mature miRNA-21 in living cells with high accuracy via cascaded toehold-mediated strand displacement reaction (TSDR) amplifications. The DNF is prepared by a simple self-assembly of six ssDNAs, and the signal probes are docked inside the DNF. Because of its rigid framework structure, the DNF shows enhanced enzyme stability. Upon entering cells, only the short target mature miRNA-21 sequences instead of the large-sized pre-miRNAs are allowed to be accommodated inside the cavity of the DNF owing to the size-discriminative capability of the DNF. The cascaded TSDR amplifications can thus be activated by the mature miRNA-21 together with endogenous ATP to result in magnified fluorescence for sensitive detection and selective discrimination of miRNA-21 from the interference pre-miRNAs. Our results indicate that the DNF probes can offer robust sensing means for detecting various intracellular mature miRNAs with high accuracy for disease diagnoses and biomedical studies.

Targeted and direct intracellular delivery of proteins plays critical roles in biological research and disease treatments, which yet remains highly challengeable. Current solutions to such a challenge are limited by...

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Accurate and specific imaging of low-abundance intracellular microRNAs (miRNAs) is crucial for monitoring cellular processes and disease diagnosis. Despite the fact that nucleic acid amplification technologies have shown great advantages for the detection of trace targets, their live cell imaging applications remain a major challenge because of the insufficient stability and slow reaction kinetics of the probes in cellular delivery and imaging. Herein, we demonstrate the synthesis of DNA-cross-linked polymeric lighting-up nanogels (DPLNs) through the DNA hairpin-based hybridization chain reaction within nanoscale-confined space for monitoring and imaging live cell miRNA-21 with high sensitivity. Cascaded catalytic hairpin assembly of two hairpin signal probes confined in the DPLNs can be triggered by the target miRNA, causing substantially amplified fluorescence resonance energy transfer signals with accelerated reaction kinetics. Moreover, the DPLNs show low cytotoxicity and highly enhanced nuclease resistance and can be successfully delivered into live cells for imaging low levels of miRNA-21. In addition, the DPLN probes can be readily tuned by specific sequences for monitoring various molecular targets in live cells for important biological and biomedical applications.

Small interfering RNA (siRNA) has increasingly evolved as a potent therapeutic solution for several pathological conditions including cancers via post-transcriptional oncogene suppression in cellular pathways. And, the key for siRNA-based...