Dual-Signal Cascaded Nucleic Acid Amplification Circuit-Loaded Metal-Organic Frameworks for Accurate and Robust Imaging of Intracellular MicroRNA

Cascaded signal amplification technologies play an importantrolein the sensitive detection of lowly expressed biomarkers of interestsyet are constrained by severe background interference and low cellularaccessibility. Herein, we constructed a metal-organic framework-encapsulatingdual-signal cascaded nucleic acid sensor for precise intracellularmiRNA imaging. ZIF-8 nanoparticles load and deliver FAM-labeled upstreamcatalytic hairpin assembly (CHA) and Cy5-modified downstream hybridizationchain reaction (HCR) hairpin reactants to tumor cells, enabling visualizationof the target-initiated signal amplification process for double-insurancedetection of analytes. The pH-responsive ZIF-8 nanoparticles effectivelyprotect DNA hairpins from degradation and allow the release of themin the acid tumor microenvironment. Then, intracellular target miRNAsorderly trigger cascaded nucleic acid signal amplification reaction,of which the exact progress is investigated through the analysis ofthe fluorescence recovering process of FAM and Cy5. In addition, DNA@ZIF-8nanoparticles improve measurement accuracy by dual-signal colocalizationimaging, effectively avoiding nonspecific false-positive signals andenabling in situ imaging of miRNAs in living cells. A dual-signalcolocalization strategy allows accurate target detection in livingcells, and DNA@ZIF-8 provides a promising intracellular sensing platformfor signal amplification and visual monitoring.