Synthesis and study of molecular interactions between phosphatidyl choline and two laminin derived peptides hydrophobically modified.

Two peptides based on the active SIKVAV sequence were synthesized and hydrophobically modified through attachment of a myristoyl residue to the amino terminal group. A comparative study was carried out on the physicochemical properties of both parent and hydrophobically modified structures. Properties studied were hydrophobicity, surface activity, spreadability on aqueous surfaces, penetration in lipid monolayers, aggregation and haemolytic activity. Results obtained indicate that myristoyl containing peptides form micelles at 10(-6) M concentration, whereas parent peptides start to aggregate at 10(-5) M. All of them are able to spread on aqueous surfaces forming stable monolayers. Concerning their haemolytic activity only one of the sequences promotes a partial lysis of erythrocytes after 30 min incubation at 37 degrees C and 10(-5) M concentration in the media.

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). Depending on the constitution of the polar phase, it is possible to obtain different kinds of formulations (gel, liquids, ...), and, depending on the different possibilities of incorporation of the polar ingredients, identical compositions can be formulated in terms of percentage of their components, but showing different rheological characteristics, allowing an adaptation to the required specific needs of formulation.

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. Selective incorporation of the polar ingredients by means of the so-called double-titration procedures was studied. Independent consideration of the polar ingredients leads to modelling of the system in a regular tetrahedron in which the components are located at the four vertices. Several possibilities of double-titration procedures are considered in the tetrahedron depending on the different sequences of incorporating the polar ingredients. The results obtained show a critical influence of the double-titration procedures on two main aspects: limits of existence of the transparent gel realms, and rheological behaviour of some selected compositions. The different possibilities compared with the fixed characteristics obtained by the conventional method of preparation constitute an advantage in adapting a final formulation to the specific needs.

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. It may be concluded, that the use of phase diagrams on cosmetic systems, constitutes a useful way to select the components and their mutual ratios, allowing an adaptation to the specific requested conditions of formulation.

Transparent formulations of a liposoluble sunscreen agent in an aqueous medium.

Synopsis Transparent formulations of a liposoluble sunscreen in an aqueous medium were studied, taking into account the different chemicals of a selected system situated in the vertices of a regular tetrahedron: sunscreen agent, co-solvent, (surfactants +/- mineral oil) mixture (in the tetrahedron base) and water as the fourth component. Several compositions were selected at optimized component ratios after which water was added progressively. Clear gel and liquid compositions were obtained yielding a sunscreen agent that it suitable for conventional use. The physico-chemical properties of some compositions were assessed in terms of water/sunscreen agent content.

Solubilization of Large Unilamellar Liposomes by Alkyl Glycosides

The study of biological membranes involves the dissociation, characterization and re-assembly of membrane components. The most important aspect of this approach is the use of an appropriate surfactant as solubilizing agent. In this work the solubilization of large unilamellar liposomes by alkyl glycosides has been studied. Solubilization of phospholipid bilayer is produced by the formation of surfactant-phospholipid mixed micelles. Some pure alkyl glycosides as well as two commercial alkyl polyglucosides have been tested. This has permitted the study of the solubilizing capacity of the phospholipidic bilayer of different alkyl glycosides as a function of their structure. Among the alkyl glycosides tested, dodecyl maltoside has shown the lowest critical micelle concentration as well as the highest solubilizing capacity, i.e., the minimal surfactant/phospholipid molar ratio in the mixed micelles.

Applications of ternary systems in specific cosmetic formulations.

Synopsis The study of ternary systems leads to the understanding of the physico-chemical aspect and allows the contribution of the different components to a cosmetic formulation to be developed. The present investigation was centred in the zone of transparent get belonging to a previously studied ternary system containing a broad variety of different structural compositions. The possibility of including an active sunscreen as well as the ability to increase the water content of the gel was studied. The microscopical study of the compositions with polarized light allowed us to assign the corresponding different structures. A correlation between these structures and their physico-chemical properties, with special emphasis to rheology, has been established.

Use of microemulsions as vehicles for nucleophilic reagents in cosmetic formulations.

Synopsis The modifications of chemical reactivity induced in the human hair during its treatment with oxidative (H(2)O(2)) or reductive (HSO(3)Na) agents via a micellar or a microemulsion system have been investigated. For this purpose, phase diagrams of micellar solutions and microcmulsions with H(2)O(2) or NaSO(3)H have been made in order to find out the corresponding areas of solubility. The properties of conductivity, surface tension and light scattering of various monophasic compositions as a function of their water content, have been studied. As a result of the chemical reactivity data of human hair obtained through the reaction of H(2)O(2) or HSO(3)Na via a micellar or a microemulsion system, it appears reasonable to predict a more effective reaction of such agents with cystine residues existing in keratinic substrates, particularly when they are applied via a microemulsion. The decrease of the water content of the compositions considered, increases chemical reactivity of the keratinic proteins favouring the formation of cysteine and of cysteic acid in the reductive or oxidative treatments respectively.