Triple-helix-mediated Nano-delivery System Construction Of Dual MicroRNAs For Synergistic Damaging Tumor Cells

Cancer is a primary disease threatening human health.The development of new and effective treatments is already urgent.With the continuous research on the mechanism of tumor development,it was found that the oncogenic miRNAs were highly expressed,while the tumor suppressor miRNAs were lowly expressed in tumor cells.By delivering inhibitors of tumor suppressor miRNAs and oncogenic miRNAs into tumor cells,the expression of protooncogenes and tumor suppressor genes in tumor cells can be more effectively coordinated.However,miRNAs are unstable and easily degraded,and it is difficult to penetrate the cell membrane.A variety of miRNA delivery systems have therefore been developed to protect the efficient delivery of miRNAs into cells.These delivery systems still present problems such as low loading,susceptibility to detachment or destruction of miRNAs.Thence,it is necessary to develop a safe and effective new miRNAs delivery system for tumor treatment.At present,most of the research is only a scientific problem of the delivery of a single type of miRNAs with limited tumor suppressive effects.DNA nanostructures have the advantages of being resistant to digestion,stability,biocompatibility,and easy modification of targeting molecules.A new strategy was developed to utilize DNA nanostructures to mediate dual miRNAs in synergistic tumor suppression.Using DNA as a skeletal chain,the suppressor of tumor suppressor miR-205 and miRNA-221 forms a nucleic acid nanostructure under the action of crystallization and dense packing of nucleic acid liquid by one-step thermal denaturation renaturation self-assembly.The nucleic acid nanostructure was characterized by "nanococoon" at atomic force microscopy and transmission electron microscopy.The polyacrylamide gel electrophoresis and stability experiments showed that the nucleic acid nanococoon had excellent anti-cutting ability and stability.It can be stable for a long time in the blood.This provides a strong guarantee for the stable delivery of miRNAs in the blood.Next,it was proved that the nucleic acid nanococoon can effectively inhibit the growth and proliferation of MDA-MB-231 breast cancer cells,but had no effect on the normal cells.Nucleic acid nanococoon has better active targeting ability with MUC-1 aptamers.The mechanism of tumor suppression is that the nucleic acid nanococoon enters the tumor cells and releases miR-205 and antagomiR-221,resulting in decreased expression of E2F1 and Snail,increased expression of E-Cadherin.Thereby,the cell cycle is prolonged,the division is slowed down,the rapid proliferation of tumor cells is suppressed,and the migration and invasion of tumor cells are effectively inhibited.The nucleic acid nanococoon can be effectively used for the synergistic treatment of tumors,and opens up a new direction for targeted delivery of miRNAs and synergistic treatment of tumors.