Preparation method of DNA rectangular pyramid for visually detecting tumor-related mRNA in living cells

The invention discloses a preparation method of a DNA (Deoxyribonucleic Acid) rectangular pyramid for visually detecting tumor-related mRNA (messenger Ribonucleic Acid) in living cells. The DNA rectangular pyramid is formed by self-assembling two capture probes and four DNA support probes with fluorescence labels through two-step annealing reaction. When the target does not exist, the rigid doublestrands of the probe are supported to enable the DNA rectangular pyramid to keep an open three-dimensional structure; and when the target exists, the target chain initiates a strand displacement reaction, and the capture probe leaves and captures the target; and meanwhile, a single chain at the bottom edge of the DNA rectangular pyramid is automatically folded to form a more stable hairpin structure, and the overall space structure of the DNA rectangular pyramid is driven to change; Cy3 and Cy5 marked at two ends of the bottom edge of the DNA rectangular pyramid get close to each other alongwith the folding process t