Abstract
Lipopolyplexes are of widespread interest for gene therapy due to their multifunctionality and high transfection efficiencies. Here we compared the biological and biophysical properties of a lipopolyplex formulation with its lipoplex and polyplex equivalents to assess the role of the lipid and peptide components in the formation and function of the lipopolyplex formulation. We show that peptide efficiently packaged plasmid DNA forming spherical, highly cationic nanocomplexes that are taken up efficiently by cells. However, transgene expression was poor, most likely due to endosomal degradation since the polyplex lacks membrane trafficking properties. In addition the strong peptide-DNA interaction may prevent plasmid release from the complex and so limit plasmid DNA availability. Lipid/DNA lipoplexes, on the other hand, produced aggregated masses that showed poorer cellular uptake than the polyplex but contrastingly greater levels of transgene expression. This may be due to the greater ability of lipoplexes relative to polyplexes to promote endosomal escape. Lipopolyplex formulations formed spherical, cationic nanocomplexes with efficient cellular uptake and significantly enhanced transfection efficiency. The lipopolyplexes combined the optimal features of lipoplexes and polyplexes showing optimal cell uptake, endosomal escape and availability of plasmid for transcription, thus explaining the synergistic increase in transfection efficiency.
Highlights
Lipopolyplexes are of widespread interest for gene therapy due to their multifunctionality and high transfection efficiencies
We have previously described LPD nanocomplex formulations for gene delivery comprising a mixture of cationic liposome (L; e.g., DOTMA/DOPE) and cationic targeting peptide (P) which self-assemble on mixing with DNA (D) at appropriate ratios[11]
The ternary combination of liposome, peptide and DNA of LPD formulations displayed a synergistic increase in luciferase transgene expression compared to binary PD and LD formulations (Figure 1)
Summary
Lipopolyplexes are of widespread interest for gene therapy due to their multifunctionality and high transfection efficiencies. Lipid/DNA lipoplexes, on the other hand, produced aggregated masses that showed poorer cellular uptake than the polyplex but contrastingly greater levels of transgene expression. This may be due to the greater ability of lipoplexes relative to polyplexes to promote endosomal escape. The lipopolyplexes combined the optimal features of lipoplexes and polyplexes showing optimal cell uptake, endosomal escape and availability of plasmid for transcription, explaining the synergistic increase in transfection efficiency. Lipopolyplex formulations that combine both liposomes and polymers have gained popularity in recent years as the mixture of components enables the formation of nanocomplexes with a wider range of functionalities than either lipoplexes or polyplexes, with higher transfection efficiencies[6,7,8,9,10]. The LPD vector was formulated with a liposome (L), made up of DHDTMA
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