Study On RNAi Regulation And SiRNA Delivery Based On Aptamer

RNA interference(RNAi)is an exogenous or endogenous double-stranded RNA that induces RNA-specific degradation of homologous target genes in vivo,leading to post-transcriptional gene silencing.It can rapidly,efficiently and specifically down-regulate the expression of the target gene,thereby inhibiting protein synthesis,inducing cell apoptosis,and therefore can be used for tumor gene therapy.However,gene therapy must be safe and effective,and exogenous RNAi vector in the cell is completely dependent on the Dicer enzyme,helicase,auxiliary identification of homologous sequence proteins and other factors,can not achieve artificial precision regulation,and may have an excess or deficiency of intracellular expression,but also has low transfection efficiency and cytotoxicity.Therefore,spatial and temporal regulation of RNAi and construction of safe and efficient delivery carrier is of significant importancefor gene therapy researches and practical applications.Recent studies have demonstrated that the comformational changes caused by the combination of ribozyme switch and small molecule ligand will regulate the ability of the ribozyme self-cleavage,and thus controlling gene expression.According to the characteristics of ligand concentration-dependent use of ribozyme switches,herein,we constructed a ligand-based HDV ribozyme switch regulator system in mammalian cells.Through the combination of ribozyme switch and theophylline small molecular ligand,control ribozyme cleavage to release the target gene siRNA precursor sequence,and then silence the expression of oncogene.This system realizes the precise regulation of RNAi at expression time and level,which provides a theoretical basis for the safe and effective application of RNAi in gene therapy of tumor.At present,there are many delivery vectors for si RNA during gene therapy,andmost of which face the problems such as low transfectioqn efficiency and cytotoxicity.In this sthdy,we present a novel enzymatic synthetic approach to produce tumour-targetable RNAi nanovectors.The RNAi nanovector is mainly composed of multiple tandem copies of siRNA precursors by rolling circle transcription(RCT),while compressing the precursor from a loose structure into dense nanoparticles to improve transfection efficiency.In addition,RNAi nanocarriers also introduce DNA aptamers for targeting cells,and the whole process does not rely on transfection reagents and reduces cytotoxicity.Therefore,the RNAi nanovector systems have great potential in the safe and effective delivery of siRNA and tumor therapy applications.