Conformational changes in stratum corneum lipids by effect of bicellar systems.

Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was applied to study the effects of the bicelles formed by dimyristoyl-glycero-phosphocholine (DMPC) and dihexanoyl-glycero-phosphocholine (DHPC) in porcine stratum corneum (SC) in vitro. A comparison of skin samples treated and untreated with bicelles at different temperatures was carried out. The analysis of variations after treatment in the position of the symmetric CH2 stretching, CH2 scissoring, and CH2 rocking vibrations reported important information about the effect of bicelles on the skin.

Formation and properties of mini-emulsions formed by microemulsions dilution.

Mini-emulsions have been formed in quaternary systems water/hexanol/sodium dodecyl sulfate/decane by dilution of a microemulsion with an excess of water. We have investigated systematically the effect of composition variables in the droplet size and Ostwald Ripening rate. This droplet size has been investigated by using dynamic light scattering of samples submitted to further dilution in water.

Selective incorporation of the polar ingredients on the formulation of clear gels through phase diagrams.

Synopsis This paper attempts to systematize the preparation of cosmetic formulations by means of phase diagrams. The general criteria used to adapt the usually complex cosmetic systems to simple ternary diagrams W/O/S, consists of grouping the different ingredients according to their functional characteristics (hydrophilics, lipophilics and amphiphilics) that are located respectively in the corresponding vertices W, O and S. Thus, the polar ingredients are always incorporated simultaneously as a single phase, over the initial combinations O/S according to the classical titration procedure.

Influence of the polar phase in the formulation of cosmetics.

Synopsis Frequently, the incoporation of the polar phase, as a second step in the formulation of a cosmetic, is considered as a simple dilution process. This work shows the influence of the polar phase on the final formulation, according to its constitution as well as the method of incorporation. Modelling the system through a regular tetrahedron suggests alternative ways to the usual method of incorporation (direct titration with a polar phase with a given composition), based on selective incorporation of the polar ingredients (double titration procedures).

Transparent gels: study of their formation and assimilation of active ingredients through phase diagrams.

Synopsis Multicomponent gel formulations capable of assimilating, simultaneously, several active ingredients of potential application in the cosmetic field were studied. The possibility of formation of a transparent gel was determined using a method which consisted in the optimization of several lipophilic basic compositions, composed of oil, a mixture of surfactants, a sunscreen agent, several vitamins and antioxidants situated in the base of a regular tetrahedron that symbolized the considered system. To this, a polar phase made of water, a cosolvent and urea in appropriate proportions and situated in the fourth vertex, was progressively added.