Light-controlled Deoxyribozyme Nanoprobes For MiRNA Inhibition In Breast Cancer Cells

MicroRNA（miRNA）is a short RNA molecule that regulates gene expression.Studies have shown that the occurrence and development of different cancers and many other pathological conditions are closely related to specific miRNA expression disorders.The conditions for the enzyme cleavage reaction of DNAzymes are mild,and the reaction can occur in the presence of metal ions and the target.Therefore,the development of ribozymes for miRNA cleavage is of great significance.So far,many different types of DNAzymes have been constructed for the detection and cutting of RNA in tumor cells,so as to achieve the purpose of gene regulation.In this paper,8-17 deoxyribozyme mediated by MnO₂ nanosheets was developed for gene regulation of miRNA in MCF-7 cells.The main contents are as follows:（1）A DNAzyme probe mediated by MnO₂ nanosheets was constructed to inhibit miR-21 in MCF-7 cells.DNAzyme-MnO₂ nanosystem can enter cells through endocytosis,and glutathione（GSH）in cancer cells can degrade MnO ₂ nanosheets into Mn²⁺.While releasing DNAzyme,it also provides assistance for ribozyme cleavage reaction.factor.DNAzyme dissociates in the cell and combines with miR-21 to cleave miR-21.Since the ability of the cleaved miR-21 to bind to the two arms of DNAzyme is weakened,it will be released,so DNAzyme can repeatedly cut miR-21 in cancer cells,continuously lowering the relative expression level of miRNA in the cell.At the same time,by detecting the expression level of B-lymphoblastoma-2（Bcl-2）protein associated with miR-21 and the cell proliferation inhibitory effect,the effect of the probe for gene regulation can be effectively evaluated.（2）A MnO₂ nanosheet-mediated photocaged DNAzyme probe was developed to inhibit miR-21 in MCF-7 cells.MnO₂ nanosheets adsorb and transport the caged DNAzyme probe into the cell through electrostat ic adsorption.The GSH in the cancer cells releases the caged DNAzyme,and the ribozyme will be locked in the absence of ultraviolet light.Only by breaking the PC-linker through ultraviolet light,can the ribozyme be"unlocked",and the ribozyme can be ac tivated under the action of the cofactor,and the miR-21 in MCF-7 cells can be cleaved cyclically.At the same time,down-regulated miR-21 further regulates Bcl-2 protein,which is an anti-apoptotic factor,and down-regulation of Bcl-2 protein can inhibit the growth of MCF-7 cells.