Gene-silencing siRNA has shown great promise for the treatment of genetic diseases,cancers,and viral infections,but its therapeutic value has been hindered by the lack of an efficient and safe in vivo delivery system to target specific cells.The motor pRNA of phi29 has a strong tendency to form dimers,trimers and hexamers by interaction of interlocking right and left hand loops.This unique feature makes pRNA an ideal vector for the delivery of multiple therapeutic RNAs.Toxicity of pRNA was detected by transfection of 8 pRNA in HeLa cells.A pRNA-based vector was designed to carry siRNAs to inhibit GFP or HBV surface gene expression.Silence effects on siRNA against expression of GFP or HBV surface gene were detected in HeLa cells.Viral replicative intermediates were detected by Southern blotting.The results of toxicity study showed there was no toxicity of pRNA to cultured monolayer cells.The siRNA connected with pRNA can inhibit GFP or HBV surface gene expression in HeLa cells and inhibit HBV replication in HepG2 cells.These data suggest that pRNA can be used as a vector for imparting stability to siRNA in vitro.
