Search

In this study, we propose a new technique for evaluating wetting and adhesion of lotions to skin using surface tension measurements, contact angle measurements and calculations based on the Owens-Wendt-Rabel-Kaelble (OWRK) method. Three prescription lotions (Napageln® Lotion 3%, Sumilu® Lotion 3% and Felbinac Lotion 3% ｢Rakool｣） and two over-the-counter lotions (Feitas® Lotion and Salomethyl® FB Lotion α) were used. Based on the dispersive and polar components of the surface free energy of Yucatan micro pig (YMP) skin, isograms of contact angle (wetting envelope) and adhesion work of the YMP skin surface were constructed. Plotting the surface tension and its polar component of lotions on this isogram revealed that it is possible to predict the wettability and adhesion of lotions to YMP skin. Such diagrams can be easily constructed even using the surface free energy of other types of skin, such as that of humans and hairless mice. This evaluation method may be applicable to other external use medicines.

We report new lecithin reverse wormlike micelles with high viscoelasticity formed using lecithin/polyglycerol fatty acid monoester (PGLFA)/oil systems. In this study, the influence of the amphiphilicity (i.e., hydrophile-lipophile balance, HLB) of PGLFA on the phase behavior and rheological properties of reverse wormlike micelles was investigated in detail. PGLFAs with degrees of polymerization of polyglycerol varying between 6-40 and constituent fatty acids with chains between 6-18 carbon atoms long were used. Partial phase diagrams of the lecithin/PGLFA/n-decane systems indicated that the appropriate PGLFA could change the lecithin/oil solution into a highly viscoelastic solution comprising reverse wormlike micelles. Rheological measurements showed that all systems that formed reverse wormlike micelles exhibited an unusual phenomenon called "shear-thickening". Furthermore, reverse wormlike micelles grew as the PGLFA concentration increased and the zero-shear viscosity (η0) of the solution rapidly increased. Our results indicate that the magnitude of the maximum η0 depends on the degree of polymerization of the constituent polyglycerol in the PGLFA, while the size of the reverse micellar region and the highly viscous region in the phase diagram depends on the HLB value of the PGLFA.

We evaluated testosterone-containing lecithin reverse wormlike micelles (reverse worms) composed of a polar substance/lecithin/isopropyl myristate for transdermal application. Water, D-ribose, or tetraglycerol were used as the polar substance and were key ingredients for forming the reverse worms. Using the reverse worms, 1 wt% of testosterone could be stably solubilized. When using D-ribose as polar substance, the maximum zero-shear viscosity of the reverse worms solution was higher than that of systems using water or tetraglycerol as the polar substance. The mechanism of skin permeation of testosterone from reverse worms solution was elucidated using skin permeation experiments with hairless mouse skin. When the structure of the reverse worms transitioned to lamellar liquid crystals at the skin/formulation interface, testosterone became supersaturated in the formulations. The structural transition occurred in systems using water or D-ribose as the polar substance, increasing the flux of testosterone. The flux of testosterone from reverse worms solution thus depends on the type of polar substance used.