| Research Abstract |
Specific targeting of therapeutic agents including peptide and gene has received a considerable impetus for effective therapy of various diseases, especially cancer. This study is aimed to develop novel vehicle system for gene targeting to achieve longevity in blood circulation, and eventually to deliver gene into target cells with high efficiency. Inspired by the nanometric-scaled core-shell structure of virus, stable and monodispersive micelles with gene-loading core were prepared through a self-assembly of poly (ethylene glycol)-poly (L-lysine) block copolymer (PEG-P(L-lysine) based oh electrostatic attraction. Plasmid DNA became highly resistant against nuclease attack by packing into the micelle core surrounded by a palisade of hydrophilic segments. From a viewpoint of utilizing these micelles as non-viral gene vector, the regulated release of DNA from the micelle is essential to achieve effective transfection. DNA release from the micelles in the cytoplasm may proceed through the exchange with the anionic compounds such as sulfated sugar. The reversible nature of PEG-P (L-lysine)/DNA micelle was further verified through the addition of polyanion, including dextran sulfate and poly-L-aspartic acid : polyanion replaced DNA in the complex with PEG-P(L-lysine), resulting in the release of free DNA in the medium. Transfection efficiency of the micelle toward cultured cells was then evaluated by luciferase assay. The micelles with excess PEG-P(L-lysine) showed an order of magnitude increase in the transfection efficiency compared to free as well as P(L-lysine)-associated plasmid DNA, indicating a promising feature of PEG-P(L-lysine)/DNA micelles as novel non-viral gene vectors. Further, various functional groups can be installed on the outer surface of the micelle so as to fix guiding molecules for a target site in the body. These results clearly featured a feasibility of polymer micelles as novel virus-inspired vehicles for gene delivery.
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