M. Eugenia Carlotti

Solid lipid nanoparticles formed by solvent-in-water emulsion-diffusion technique: development and influence on insulin stability.

Insulin-loaded solid lipid nanoparticles (SLN), obtained by the solvent-in-water emulsion–diffusion technique, were produced using isovaleric acid (IVA) as organic phase, glyceryl mono-stearate (GMS) as lipid, soy lecithin and sodium taurodeoxycholate (TDC) as emulsifiers. IVA, a partially water-miscible solvent with low toxicity, was used to dissolve both insulin and lipids. SLN of spherical shape were obtained by simple water dilution of the O/W emulsion. Analysis of SLN content after processing showed interesting encapsulation efficiency with respect to therapeutic doses; moreover, insulin did not undergo any chemical modification within the nanoparticles and most of it remained stable after incubation of the SLN with trypsin solution. The biological activity of insulin, i.e. the ability to decrease glycemia in rats, was not negatively influenced by the SLN production process, as after subcutaneous administration of insulin extracted from SLN to animals, the blood glucose levels were quite similar to those obtained after administration of a conventional insulin suspension. Consequently, SLN seem to have interesting possibilities as delivery systems for oral administration of insulin.

W/O/W Multiple Emulsions for Dermatological and Cosmetic Use, Obtained with Ethylene Oxide Free Emulsifiers

W/O/W multiple emulsions with ethylene oxide free emulsifiers, compatible with the skin, were prepared. They were fresh and easy to spread on the skin. The emulsion showed a shear thinning flux. Their multiplicity was confirmed with optical microscope analysis. FeSO4 and K3Fe(CN)6, when introduced separately in the inner and outer aqueous phases of the emulsions, did not give coloration, but when introduced together in the same aqueous phase, give a blue color due to their reaction. This experiment confirmed the multiplicity of these systems. The external aqueous phase of the emulsions was confirmed by Brilliant Blue up take from one of the multiple emulsions prepared higher than that from its W/O primary emulsion. The stability of the systems was confirmed by tests of breaking to centrifuge, of storage at 40°C and by freeze‐thaw cycles.

Effect of Some Additives Used in the Cosmetic Field on the Photocatalytic Activity of Rutile

ABSTRACT The effects of some treatments used in cosmetics to reduce the activity of titanium dioxide towards the degradation of organic compounds are reported. These treatments, which include the use of organic additives and of inorganic surface coating, are aimed to protect the components of sunscreen formulations, and also the skin, from the photocatalytic processes induced by TiO2 UV absorption. The effect of the addition of 1,3-butanediol (organic treatment) on the degradation rates of phenol, benzoic acid, and salicylic acid upon UV-A irradiation of rutile is assessed and discussed. About the inorganic coating, the effect of the surface treatment with Al2 O3 on the photocatalytic activity of rutile towards both phenol and salicylic acid is evaluated. The organic and the inorganic treatment are both very effective in inhibiting phenol degradation, but ineffective in avoiding degradation of salicylic acid. The results indicate that the degradation tests of both phenol and salicylic acid can be a useful tool for the evaluation of the efficiency of treatments aimed at reducing the effects that titanium dioxide photoactivity has on cosmetic formulations.

Deformable Liposomes as Topical Formulations Containing α‐Tocopherol

Several deformable liposomes were formulated using hydrogenated soya lecithin and sodium cholate, polisorbate 80, dipotassium glycyrrhizinate, or saccharose monopalmitate. The lipid:surfactant w/w ratio necessary to obtain elastic vesicles depended on the O/W surfactant and ranged from 4∶1 to 20∶1. The liposomes obtained were able to entrap α‐tocopherol and tocopheryl acetate up to 0.17% w/w. Elastic liposomes, whose deformability was confirmed by filtration through microporous filters and differential scanning calorimetry measurements, when non‐occlusively applied on pig ear skin, determined negligible skin fluxes of α‐tocopherol, while skin deposition significantly increased compared with reference solutions or normal liposomes. Moreover, the entrapment of the vitamin either in elastic or in normal liposomes increased its photo‐stability under UVB irradiation.

Behavior of Some Rheological Modifiers Used in Cosmetics Under Photocatalytic Conditions

Abstract This work studies the photocatalytic degradation of some water‐dispersed rheological modifiers upon UV irradiation of suspended TiO2, an inorganic pigment used as sunscreen in solar creams and gels. The photocatalytic activity of titanium dioxide is a matter of concern in the field of cosmetics, since it causes the undesired photoinduced degradation of organic compounds. The glyceryl polymethacrylate + propylene glycol Lubrajel® DV showed a lower decrease in viscosity than cellulose derivatives upon irradiation in the presence of TiO2, most likely due to higher stability under photocatalytic conditions. As a consequence, use of Lubrajel instead of modified cellulose is preferable when the photocatalytic stability of the rheological modifier is an important issue. Moreover, the degradation of phenol and salicylic acid, chosen as model organic molecules, was studied in the presence of both TiO2 and the modifiers under illumination. The purpose was to assess the photocatalytic activity of titanium dioxide under conditions simulating those of the real cosmetic product. The presence of the rheological modifiers protects both phenol and salicylic acid from photocatalytic degradation.

Photocatalytic Activity of Inorganic Sunscreens

Some inorganic pigments are used as ingredients for sunscreens as they can absorb, reflect or scatter UV radiation. Titanium dioxide and zinc oxide, which are used for this purpose, are semiconductor oxides and show photocatalytic activity. As a consequence, they can promote transformation of organic molecules upon absorption of radiation. This work studies the activity of some of these pigments, provided by cosmetic producers, towards phenol, chosen as a model aromatic molecule. An attempt is made to explain the different activity of the various pigments, coated or uncoated, towards phenol.

Synergistic action of vitamin C and amino acids on vitamin E in inhibition of the lipoperoxidation of linoleic acid in disperse systems

Abstract The synergistic effect of some amino acids ( l -tryptophan, l -cysteine, l -alanine and glycine), glutathione, n -butylamine and of vitamin C on the antioxidant effect of vitamin E on the lipoperoxidation of linoleic acid in sodium dodecylsulphate micellar solutions and oil in water emulsions was examined at pH 5.0 and 7.0. The antioxidant activity of vitamin E, measured by oxygen consumption, was similar in both emulsions and micellar solutions. The addition of vitamin C produced only a slight synergistic effect at pH 5.0 and none, or a prooxidative effect, at pH 7.0. The amino acids studied exerted a synergistic effect only at pH 5.0, and their effectiveness was partially related to their lipophilicity.

Inhibition of the photocatalytic degradation of benzoic and salicylic acid by nontoxic aromatic compounds

This work studies the photocatalytic degradation of benzoic (HBz) and salicylic acid (HSal) in the presence of nontoxic aromatic compounds (phenylalanine, tyrosine, tryptophan, and sodium benzenesulfonate). The purpose is to find compounds able to compete for electron‐transfer processes in photocatalysis: the failure to do this is one of the main drawbacks of currently adopted sunscreens. Sodium benzene sulfonate (SBS) proved to be quite effective in inhibiting electron transfer as demonstrated by its effect on the photocatalytic degradation of HBz and HSal. Furthermore, a mixture of SBS and 1,3‐butanediol was able to inhibit the photocatalytic degradation of both phenol and HBz. This fact indicates that the mixture is able to block both the hydroxylation pathway (responsible for phenol degradation) and the electron‐transfer one (HBz degradation). The simultaneous inhibition of the degradation of both phenol and HBz has not been observed in commercial sunscreen treatments. This work thus shows that the use of nontoxic aromatic compounds can be a way to improve sunscreen performance, and that the photocatalytic degradation test of phenol+HBz (or phenol+HSal) is the most appropriate way to find the best performing treatments.

Formulation of Dry Emulsion for Topical Applications

Dry emulsions were investigated for their possible use in cosmetic and pharmaceutical fields and an extract of Vitis vinifera leaves was obtained and characterized in terms of quality and quantitative levels, which can be introduced in a selected dry emulsion formulation. Several pre-dry emulsions were prepared, six of which were chosen as a consequence of their satisfying physico-chemical and over-time stability characteristics. They were successively freeze-dried and reconstituted after optimising the reconstitution modalities and characterized by optical microscopy, granulometric and thermal analysis, FTIR analysis, rheology, and texture studies. The best formulation was chosen to introduce Vitis vinifera dry extract prepared by percolation: a fair increase in anthocians stability was noted over time in dry emulsions as compared with classic emulsions.

Interaction of sodium lauroyl glutamate and potassium lauroyl hydrolyzed collagen with hydroxypropyl methyl cellulose

Abstract Hydroxypropyl methylcellulose (HPMC) was used to increase the viscosity of aqueous solutions of sodium lauroyl glutamate (SLG) and potassium lauroyl hydrolyzed collagen (KLHC), as viscosity modifiers commonly used in toiletry products fail to thicken in the presence of these surfactants. A surfactant–polymer link was indicated by a change of surface tension as a function of surfactant and polymer concentration and by viscosity trends of surfactant–polymer mixtures around critical micellar concentration (CMC). A positive surfactant–polymer interaction was suggested by an experimental design of Doehlert. Such an interaction affects the viscosity of the system and the solubility of two lipophilic dyes in the micellar core of the surfactant–polymer complexes. Hydroxypropyl methylcellulose prevents SLG precipitation by lowering its Kraft point.