Formation of lens-like vesicles induced via microphase separations on a sorbitan monoester membrane with different headgroups

Effect of dehydrocholic acid conjugated with a hydrocarbon on a lipid bilayer composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine

The effects of bile acids, dehydrocholic acid (DHA) and DHA conjugated with a hydrocarbon (6-aminohexanoate; 6A-DHA) were evaluated using a lipid bilayer composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). DOPC formed a homogenous thin membrane in presence or absence of the DHA, while 20 mol% 6A-DHA induced phase separation on the DOPC thin membrane. It was observed formation of a stomatocyte-like liposomes when these membranes were suspended in a basic solvent. Generally, liposome formation can be prevented by some bile acids. It was found that DHA and 6A-DHA did not disrupt liposome formation, while DHA and 6A-DHA perturbed the liposomal membrane, resulting in increased local-fluidity due to the bent structure of DHA and 6A-DHA. DHA and 6A-DHA showed completely different effects on the hydrophobicity of the boundary surface of DOPC liposome membranes. The steroidal backbone of DHA was found to prevent the insertion of water molecules into the liposomal membrane, whereas 6A-DHA did not show the same behavior which was attributed to its conjugated hydrocarbon.

Solubility and bioavailability enhancement study of lopinavir solid dispersion matrixed with a polymeric surfactant - Soluplus

As a biopharmaceutical classification system Class IV drug, lopinavir (LPV) shows relatively poor water solubility and permeation in vivo. In the study, we developed novel solid dispersions (SD) of LPV to improve its bioavailability and to describe their overall behaviors. By employing solvent evaporation for a preliminary formulation screening, the SDs of LPV-polymer-sorbitan monolaurate (SBM, as the wetting agent) at 1:4:0.4 (w/w) dramatically enhanced the LPV dissolution in a non-sink medium, and then hot-melt extrusion (HME) was applied to improve the dissolution further. A hydrophilic polymer - Kollidon VA 64 (VA64) and a polymeric surfactant Soluplus were employed as matrix respectively in the optimized formulations. The dissolution profiles of extrudates were significantly higher than those of SDs prepared with solvent-evaporation method. It was attributed to the stronger intermolecular interactions between LPV and the polymers in the HME process, which was also supported by the stability analysis after 6 months storage under 25 °C/60% RH. The differential scanning calorimetry, fourier transform infrared spectroscopy and equilibrium studies showed VA64 only created hydrogen bonding (H-bond) with LPV, but Soluplus generated both H-bond and micelle thanks to its amphiphilic structure. In addition, the bioavailability of LPV in Soluplus matrixed extrudate was 1.70-fold of VA64 matrixed extrudate and 3.70-fold of LPV crystal. In situ permeability and Caco-2 cell transport studies revealed that Soluplus significantly enhanced the permeability of LPV through rat intestine and Caco-2 cell monolayers by P-glycoprotein (P-gp) inhibition. Herein, Soluplus matrixed extrudate improved the LPV bioavailability through three mechanisms: H-bond with LPV, micelle formation in water and P-gp inhibition in vivo. These unique advantages of Soluplus suggested it is a promising carrier for poorly water soluble drugs, especially the substrates of P-gp.

Characterization of sorbitan surfactant-based vesicles at the molecular scale using NMR: Effect of acyl chain length vs. phospholipid composition

We focused on the characterization of the hydrophobic-hydrophilic interface of the membrane of vesicles prepared with various sorbitan surfactants using two evaluation methods: Laurdan fluorescence intensity (GP(340) value) and NMR analysis (half linewidth). Laurdan fluorescence intensity analysis, used to evaluate the hydrophobicity of the interior of the vesicular membrane, indicated a similarity between Span vesicles and liposomes in terms of hydrophobicity, while NMR analysis, used to assess the mobility of lipid molecules, indicated a large difference between Span vesicles and liposomes in terms of molecular mobility at the interface. These results suggest that the physicochemical properties of Span vesicles and liposomes are roughly similar at the "meso-scale" but not completely similar at the "molecular scale."