Transfection efficiency of pORF lacZ plasmid lipopolyplex to hepatocytes and hepatoma cells

Combined Use of Polycationic Peptide and Biodegradable Macromolecular Polymer as a Novel Gene Delivery System: A Preliminary Study

Plasmid(p) DNA was condensed by polycationic peptide polylysine (PLL) to be a core and then encapsulated in biodegradable monomethoxy (polyethyleneglycol)-poly(lactide-co-glycolide)-monomethoxy (poly-ethylene glycol) (PELGE) to form core-shell nanoparticles as a novel gene delivery system PPD (PELGE-PLL-DNA). Nanoparticles formed from PPD had several complementary properties such as improved biocompatibility, decreased cytotoxicity, enhanced pDNA integrity, and the characteristic of lysosomal escape as PLGA nanoparticles. The results demonstrated the potential of this PPD as an efficient gene delivery system.

Nuclear localisation and pDNA condensation in non-viral gene delivery

BACKGROUND

Non-viral gene delivery vectors are multi-component systems reflecting various functionalities required for effective cell transfection, including DNA condensation, promotion of cell membrane interactions and provision for subcellular targeting through endosomal escape and/or nuclear delivery. Elements mediating these functions will clearly display inter-dependency. In this study we sought to explore the relationship within non-viral vectors of condensation and nuclear localisation.

METHODS

Binary, tertiary and quaternary vectors were prepared with combinations of pDNA, DOTAP lipid, the polycation peptide protamine and either SV40 nuclear localisation sequence peptide ('SV40 NLS') or a one amino acid substituted mutant of SV40 NLS ('mutant sequence'). The efficiency of pDNA condensation was determined by gel electrophoresis and quantitative fluorescence spectroscopy. Transfection efficiency was examined in mammalian cells in vitro using standard methods, by electroporation to bypass the plasma membrane barrier and in cells arrested in G0/G1 cell cycle phase to examine the effect of cell division and nuclear membrane disruption.

RESULTS

Small NLS peptide sequences, despite possessing a significant proportion of basic amino acids, display minimal pDNA-condensing ability when compared to larger polycations such as protamine. In standard in vitro cell adherent transfection studies the predominant elements affording enhanced gene expression were effective pDNA condensation and lipid enhancement of cell membrane interactions. These features conversely hinder efficient gene expression in cells that have undergone electroporation. The benefit of SV40 NLS was only apparent when used in non-dividing cell populations.

CONCLUSIONS

Whilst effective levels of non-viral-mediated gene expression generally rely on efficient condensation of pDNA and enhanced interactions with cellular membranes, non-covalently associated NLS within a multi-component non-viral gene vector appears to contribute benefit in sustaining gene expression in non-dividing cells.

Targeted gene delivery to hepatoma cells using galactosylated liposome-polycation-DNA complexes (LPD)

A major goal for gene therapy is to obtain targeted vectors that transfer genes efficiently to specific cell types. The liver possesses a variety of characteristics that make this organ very attractive for gene therapy. In the present study, four cholesterylated thiogalactosides 1a approximately d with different spacer length were synthesized to formulate novel lipid-polycation-DNA (LPD) complexes, which were composed of galactosylated cationic liposomes, protamine sulfate and plasmid DNA. The galactosylated LPD1c significantly improved the levels of gene expression in cultured hepatoma cells HepG2 and SMMC-7721, while LPD1a and LPD1b did not significantly improve the levels compared with non-galactosylated LPD. Meanwhile, increased transfection activity was not observed in mouse fibroblasts L929 for galactosylated LPDs. Cytotoxicity of galactosylated LPDs assay showed they had no obvious toxicities to L929 cells and HepG2 cells. In summary, the length of the spacer between the anchor and galactose residues was important for the recognition of asialoglycoprotein receptor. The LPD1c described here, combining the condensing effect of protamine and the targeting capability of cholesterylated thiogalactosides, are potentially useful gene carriers to liver parenchymal cells.

PELGE Nanoparticles as New Carriers for the Delivery of Plasmid DNA

Biodegradable monomethoxy(polyethyleneglycol)-poly(lactide-co-glycolide)-monomethoxy(poly-ethyleneglycol) (PELGE) copolymers were synthesized by ring-opening polymerization to formulate plasmid DNA loaded nanoparticles. A double emulsion method with polyvinyl alcohol as the emulsifier in the external aqueous phase was employed to prepare nanoparticles. The effects of monomethoxypoly(ethyleneglycol) (mPEG) segments in the polymer on particle size, zeta potential, encapsulation efficiency and in vitro release were investigated. It was found that the introduction of a certain amount of hydrophilic mPEG segments in the copolymer chains could improve the affinity of copolymer with plasmid DNA and enhance the emulsification ability of the copolymer. Thus DNA loaded nanoparticles with smaller particle sizes and higher encapsulation efficiencies were obtained by using PELGE copolymer as the matrix.