Development of PIG micelle vector system for gene delivery

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1) By the investigation into the intracellular mechanisms under confocal microscopy using fluorescence resonance energy transfer (FRET), it was revealed that fast endosomal escape and subsequent smooth disintegration of LPEI/pDNA in the cytoplasm are likely to be determining factors for the excellent transfection efficiency of this polyplex system.2) By the investigation from a physicochemical viewpoint to get insight into the structural feature of the PIC micellar vector system, PIG micelle took virus-comparable size (B100 nm) with a serum-tolerable property. The PEG-PLL (12-48)/pDNA micelles showed a gene expression comparable to the lipofection toward cultured 293 cells.3) Based on the observation of the relationship among the PIG micelle structure, physicochemnical properties, and the biological functions, new block copolymers were newly synthesized from PEG-poly(□-benzyl L-aspartate) block copolyiner (PEGPBLA) through aminolysis reaction. They have characteristics of possessing two distinct amino groups with different pKa in a side chain, i.e. one for counterparts with nucleic acids through electrostatic intcraction and the other for the buffering capacity in acidic environments such as endosomes. The transfections using these copolymers revealed their excellent efficiencies even without any endosomolytic agents such as chioroquine. It is indicated that this system has a promising feasibility for in vivo therapeutic applications owing to the proton sponge effect as well as the sufficient serum tolerability.