Tetrahedral-modified magnetic nanorobotic probe for enhanced imaging of cancer-related miRNA.

Sensitive and rapid imaging of intracellular cancer-related miRNA holds great potential for early diagnosis and treatment monitoring of cancer. However, most imaging probes are constructed on nanoparticles that rely on passive diffusion to interact and bind with the target substance, resulting a long response time and a low target recognition capability due to the solution viscous resistance. Herein, we reported a DNA tetrahedral-modified magnetic nanorobotic probe (MNP) that performed framework nucleic acid-located catalytic hairpin assembly (CHA) reaction on the surface of magnetically driven nanorobot. The tetrahedral structure not only endowed the MNP with extremely high structural stability and perfect cell-uptake performance, but its spatial confinement effect made the signal amplification of the hairpin cascade more rapid and efficient. Additionally, the active movement of MNPs enhanced the micro-mixing of fluids and accelerated target capture, significantly reducing reaction time and improving reaction kinetics. This strategy exhibited the enhanced fluorescence signal and can accurately distinguish between miR-21 and various other miRNA sequences. Moreover, the feasibility and versatility of MNPs were also successfully verified in normal and various cancer cells imaging. Therefore, the proposed MNPs are promising candidates for the detection of intracellular biomarkers and extend the design space of self-propelled micro/nanorobots in the field of cancer diagnosis and therapy.