Establishment of MicroRNA delivery system by PP7 bacteriophage-like particles carrying cell-penetrating peptide

MicroRNAs have great therapeutic potential in cancer and other diseases. However, their instability and low in vivo delivery efficiency limits their application. Recombinant PP7 bacteriophage-based virus-like particles (VLPs) could protect microRNAs against rapid degradation by RNase by packaging specific exogenous pre-microRNAs using the pac site. Insertion of a cell-penetrating peptide (CPP) into the AB-loop of VLPs could significantly improve the delivery efficiency of microRNAs into mammalian cells. Unlike other microRNA delivery methods (viral or non-viral vectors), recombinant PP7 VLPs carrying a CPP and microRNA could be efficiently expressed in Escherichia coli using the one-plasmid double expression system. Here we showed that PP7 VLPs carrying a CPP penetrated hepatoma SK-HEP-1 cells and delivered the pre-microRNA-23b, which was processed into a mature product within 24 h; a concentration of 10 nM was sufficient for the inhibition of hepatoma cell migration via the downregulation of liver-intestine cadherin expression. Furthermore, PP7 VLPs carrying a CPP and a pre-microRNA were not infectious, replicative, or cytotoxic. Therefore, recombinant PP7 VLPs can be used for simultaneous and targeted delivery of both microRNAs and peptides because of their ability to package specific exogenous RNA using the pac site and to display peptides.