Hairpin cascade circuits on programmable DNA-nucleated spherical nucleic acid for intracellular targeted microRNA imaging

•Urchin-like DNA nanostructure nucleated spherical nucleic acid was easily-prepared.•All-in-one DSNA owned self-delivery ability for cell internalization.•DSNA with excellent biostability ensured accurate target imaging in living cells.•The hairpin probes sticked on UDNs improved reaction rates and efficiency.•Target miRNA executed the hairpin cascade circuits (HAC) for amplified imaging.