Herein, we review and summarise the development and biological applications of DNA tetrahedron, including cellular biosensors and drug delivery systems.

Here, we have developed a localized catalytic hairpin assembly (LCHA) strategy for intracellular miR-21 imaging by using DNA nanowires confining both hairpin probes in a compact space.

We have designed dual-microRNA-controlled cascaded logic DNA circuits for cancer cell subtype identification. The basic idea is to improve sensitivity by cascading DNAzyme and hybridization chain reaction (HCR), and improve accuracy by simultaneous detection of miR-122 and miR-21.