Bacteriophage phi29 DNA packaging motor is a powerful bio-nanomotor driven by six pRNA molecules that bind to the connector and use ATP as the energy source. We have been able to synthesize each component and construct a switchable imitating DNA-packaging motor in vitro by coordinated self-assembly. Conformational changes and sequential action of the RNA ensure continuous rotation of the motor, while addition of ATP analogue or ATP can manually turned off or on the motor.

The global 3D structures of the motor including pRNA have been demonstrated. pRNA's size and shape can be controlled and manipulated at will to form stable dimers, trimers and arrays. The head-tail connector protein of phi29 is a 12-fold symmetric dodecamer of gene product 10 (gp10), which can self-assemble into connectors, rosettes and arrays under certain conditions. We have constructed various mutants of gp10 with additions of His tag and/or Strep tag for the facilitation of purification and truncations to either N or C-terminus. The extended tags have potential applications in the conjugation of other therapeutic molecules without compromising the activity of the motor.

pRNA is a promising tool to be used in nanodevices, pathogen detection and gene delivery due to its structural versatility, perfect size range and protein-free quality. It can form a variety of ordered, repeating structural arrays, and the polyvalent pRNA can harbor up to six therapeutic and receptor-binding molecules for the delivery to specific cancer cells. The 30-40 nm nanoparticles fulfill the size requirement for endocytosis, with longer retention time than molecules smaller than 20nm and better deliverability than particles larger than 100 nanometers. Use of such protein-free nanoparticles could avoid the immune response and prevent the rejection after repeated long-term drug administration.