Fabrication of polyvalent therapeutic RNA nanoparticles for specific delivery of siRNA, ribozyme and drugs to targeted cells for cancer therapy

Bacteriophage phi29 DNA packaging motor is geared by a six-pRNA ring. pRNA is able to form a multimeric complex and patterned superstructures via the interaction of two reengineered interlocking loops. This unique feature makes it an ideal polyvalent vehicle for nanomachine fabrication, pathogen detection, and the delivery of therapeutics. This report describes novel approaches for the fabrication of polyvalent therapeutic pRNA nanoparticles, especially tetramers for specific siRNA delivery to cancer cells and for the silencing of targeted genes. RNA 3-D design, circular permutation, folding energy alteration, and nucleotide modification were applied to generate stable RNA nanoparticles with low toxicity. Animal trials demonstrated the high efficiency of the polyvalent RNA nanoparticles in the prevention and treatment of cancer. Using such protein-free nanoparticles as therapeutic reagents would allow for long-term administration to avoid the induction of antibody due to repeated treatment for chronic diseases.