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A comparative study of the micellization of two nonionic compounds with short alkyl chains, hexanediol-1,2 (HD-1,2) and octanetriol-1,2,3 (OT-1,2,3), in aqueous solutions has been made by using the techniques of static and dynamic light scattering, refractometry, microcalorimetry, densimetry, tensiometry, and infrared spectroscopy in the frequency range of the stretching bands of C-H bonds. For HD-1,2 all the techniques used have shown a micellization. From light scattering the micelles of HD-1,2 have an aggregation number of 20, a micellar mass of 2330, a diffusion coefficient of 11.87 X 10'7 cmJ*s~', and a hydrodynamic radius of 13.5 A. Surface tension measurements and infrared spectroscopy confirmed the micellization of OT-1,2,3 previously reported by our group. We discuss the case of HD-1,2 at very high concentration.

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We have investigated the delivery and the pathway in tumoral MCF7 cells of DNA carried by liposomes prepared from (trimethyl aminoethane carbamoyl cholesterol iodide (TMAE-Chol), a cholesterol-based cationic lipid with a quaternary ammonium on the polar head. The structure of DNA-liposome complexes depends on the length of DNA and on the lipid-DNA charge ratio X. Spherical beads constitute fine structures of the observed complexes even when they appear as aggregates. For oligonucleotide transfer, dissociation from liposomes after transfection, penetration of the oligonucleotides into nuclei, and a long resident time were observed. For plasmid transfer, a correlation between the variation in the transfection level and the ultrastructure of complexes was demonstrated. The results showed a cellular route of lipid/plasmid complexes from the beginning by endocytosis, entrapped into endosomes, released by the latter until entry in the perinuclear area, and then penetration of plasmids inside the nuclei resulting in the observed expression of the beta-galactosidase gene.

The progress of research in gene therapy allows hope for treatment of mitochondrial genetic disorders provided that efficient methods for gene transfer into mitochondria can be found. In this work, we have used an oligonucleotide coupled covalently to a mitochondria-targeted peptide at one end and a cationic liposome prepared from trimethyl aminoethane carbamoyl cholesterol iodide (TMAEC-Chol) to carry it in living cells. With a fluorescent probe to label the oligonucleotide at the other end and by means of confocal microscopy, we show that such modified oligonucleotides complexed to liposomes enter into the cytoplasm of human fibroblasts in primary culture, and then, after dissociation from the complexes, they penetrate into the mitochondria. The fluorescence was still observed after 8 days, suggesting the continued presence of oligonucleotides. At the concentrations used for this study, the cationic liposomes have practically no effect on cell growth, as revealed by the MTT assay.

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