Bioswitchable Delivery of microRNA by Framework Nucleic Acids: Application to Bone Regeneration

MicroRNAs (miRs) play an important role in regulating gene expression. Limited by their instabilities, miR therapeutics require delivery vehicles. Tetrahedral framework nucleic acids (tFNAs) are potentially applicable to drug delivery because they prominently penetrate tissue and are taken up by cells. However, tFNA-based miR delivery strategies have failed to separate the miRs after they enter cells, affecting miR efficiency. In this study, an RNase H-responsive sequence is applied to connect a sticky-end tFNA (stFNA) and miR-2861, which is a model miR, to target the expression of histone deacetylase 5 (HDAC5) in bone marrow mesenchymal stem cells. The resultant bioswitchable nanocomposite (stFNA-miR) enables efficient miR-2861 unloading and deployment after intracellular delivery, thereby inhibiting the expression of HDAC5 and promoting osteogenic differentiation. stFNA-miR also facilitated ideal bone repair via topical injection. In conclusion, a versatile miR delivery strategy is offered for various biomedical applications that necessitate modulation of gene expression.