Können einkettige perfluorierte Amphiphile allein Vesikel und andere organisierte supramolekulare Verbände bilden?

Characterization of phospholipid+semifluorinated alkane vesicle system

The aim of this study is to characterize vesicles obtained by the incorporation of the semifluorinated alkane, (perfluoro-n-hexyl)ethane (diblock F6H2) to a standard lipid, egg yolk phosphatidylcholine (PC). Large unilamellar vesicles (LUVs), prepared by extrusion, were characterized by fluorescence spectroscopy, zeta potential (zeta-potential) and light scattering. By using the fluorescence spectroscopy technique, the anisotropy of l,6-diphenyl-l,3,5-hexatriene (DPH) probe at different temperatures was determined. It was demonstrated that F6H2 is placed inside of the lipid bilayer and that the hydrocarbon acyl chain in the bilayers has higher viscosity in the presence of fluoroalkane. The zeta-potential of the PC-F6H2 system is negative and increases (in absolute value) from -10 to -19 mV when the temperature rises from 10 to 25 degrees C, this last value keeping practically constant with a further increase of temperature. The adsorption of K+ ions on the liposome surface was measured by zeta-potential. This adsorption originates a sudden increase of the initial zeta-potential followed by a slight decrease with K+ concentration. The application of the DLVO theory of colloidal stability showed a growing dependence of the DLVO potential with K+ concentration and consequently a increasing stability.

Hydrolysis of DMPC or DPPC by pancreatic phospholipase A2 is slowed down when (perfluoroalkyl) alkanes are incorporated into the liposomal membrane

The effect of the incorporation of linear (perfluoroalkyl)alkanes (CmF2m + 1CnH2n + 1, FmHn) into liposomes made of DMPC or DPPC on the activity of porcine pancreatic phospholipase A2 was investigated. A large decrease in enzyme activity and modifications of the kinetic profile, especially at and above the phospholipid's phase transition temperature, were observed; both depend on the relative lengths of the phospholipid's fatty acid chains and of the Hn segment of the FmHn molecule. With DMPC Hn must have a minimum of 10 carbon atoms to be effective, as in F6H10, F8H10 and F4H12; F8H8 had no significant hydrolysis-rate-reducing effect. With DPPC Hn must have a minimum of 12 carbon atoms, as in F4H12, while F8H8, F6H10 and F8H10 were ineffective. The absence of effect when C10H22 or C16H34 was incorporated establishes that the fluorinated segment, although its length (from C4 to C8) is not crucial, is required to hinder hydrolysis by PLA2, indicating that this segment plays an important role in structuring the liposomal membrane.

Double-tailed perfluoroalkylated glycolipids as components for drug delivery and targeting systems. Preliminary biocompatibility results

Vesicles are being investigated as drug carriers, especially for enhancing the therapeutic effectiveness of the drug while minimizing its side effects. Drug targeting can be achieved if there is a specific recognition of the vesicle's outer wall by specific cells. With these objectives in mind new glycolipids fitted with fluorinated, hydrogenated or mixed, single and double-tails, containing either a gluco- or a galactopyranose residue in their hydrophilic head, were synthesized and their ability to achieve self-organized supramolecular systems was assessed. Replacement of hydrogen by fluorine in these glycolipids was found to enhance biological tolerance. Thus, a fluorinated single-tailed glycolipid displayed no action on red blood cells at concentrations as high as 50 g/l while its hydrogenated analog was hemolytic at 5 g/l. 100% of survival was obtained one month after intravenous or intraperitoneal injection into mice of isotonic dispersions of single and double-tailed glycolipids at a dose of 500 mg/kg. These glycolipids were innocuous on Namalva cell cultures at a concentration of 0.1 g/l.