Nuclear localization of cationic solid lipid nanoparticles containing Protamine as transfection promoter

Protamine has attracted much attention as DNA condenser and nuclear transfer enhancer although theexcess of hydrophilicity and the strong DNA pack restrain its potentialities. In order to overcome this lim-itation, we added Protamine in the composition of solid lipid nanoparticles (SLN-Protamine) and we com-pared this carrier with the same kind of SLN containing Esterquat 1 instead of Protamine (SLN-EQ1).Carriers cytotoxicity was assessed on COS-I cells evaluating the cell cycle by propidium iodide test, whilethe transfection efficiency was studied using pEGFP as plasmid model. The cell penetrating activity ofProtamine inside the lipid vectors was evaluated studying cell internalization by confocal microscopyusing Red Nile-labeled carriers. SLN-Protamine:pDNA showed a mean diameter five-times smaller thanthe size of SLN-EQ1:pDNA and a remarkably lesser cytotoxicity. Transfection by SLN-Protamine:pDNAwas seven-times more effective compared with the Protamine:pDNA polyplexes while no transfectioncapacity was observed for SLN-EQ1:pDNA complexes due to their inability to be internalized owing totheir larger dimension. Red Nile-SLN-Protamine were localized in endocytic-like vesicles into the nuclearmembrane suggesting the inclusion of Protamine in nano-lipophilic systems may enhance the reductionin the complex dimensions, the nuclear pDNA translocation and the pDNA release in the cell