Toward Milder Personal Care Cleansing Products: Fast ex vivo Screening of Irritating Effects of Surfactants on Skin Using Raman Microscopy

We report a novel Raman technique that allows fast and reliable ex vivo assessment of the irritability of personal care cleansing products to the skin in terms of the molecular-level effects such as retention of water by corneocytes, change in the packing order and content of intercellular lipids, and the structure of keratin. We test this technique for the single surfactants (dodecyl glucoside, sodium dodecyl sulfate, sodium cocoyl glycinate, lauramidopropyl betaine) that are typically used in personal care, as well as on three types of commercial soap bars (“superfat”, “syndet”, and “combar”). We find that soaking of the skin for prolonged time in pure water can cause unfolding of keratin, which is commonly considered as a signature of “harshness” when dealing with the surfactant formulations. Moreover, molecular-level signatures of irritability of the test surfactants and soaps at brief (10 min) exposure times do not follow the trend expected from their critical micelle concentrations (CMC) and collagen swelling. In particular, dodecyl glucoside has positive impact on the barrier properties of the stratum corneum (SC) and apparent detergency properties (solubilizes lipids without affecting their packing order). We also find that two qualitatively different soap bars (“superfat” and “syndet”) are similarly mild under the conditions studied, while the “combar” soap has detergency properties. These results demonstrate that to improve methodology of predicting irritability of a surfactant-based formulation, we need to study more systematically the molecular-level responses of the SC to exposure.

Effect of molecular weight of polyvinylpyrrolidone on the skin irritation potential and properties of body wash cosmetics in the coacervate form

Body wash cosmetics are among the most common groups of cosmetics used by consumers. Faced with strong competition in the marketplace, cosmetic manufacturers search for innovative solutions both in terms of product composition and form. An example of an innovative technology which can be used in the production of body wash cosmetics is the process of coacervation which yields a concentrated body wash product. Another important aspect which needs to be considered in the formulation of body wash cosmetics is their safety of use. It is crucial to ensure that such cosmetic products do not induce skin irritations. At present, the most widespread method of reducing the skin irritation potential of cosmetic products is the use of surfactant mixtures. The study is an attempt to evaluate the effect of using polyvinylpyrrolidone in the formulations of model body wash cosmetics in the coacervate form on the skin irritation potential and basic quality determinants of body wash products. Polyvinylpyrrolidone was found to contribute to a significant reduction in the irritant effect, and the skin irritation potential decreased in proportion to increasing molecular mass of the polymer. The application of polyvinylpyrrolidone with the different molecular weight also has an impact on improving the foaming properties of model body wash cosmetics and the stability of foam they produce.

Effect of Molecular Weight of Polymers on the Properties of Delicate Facial Foams

Body wash cosmetics are among the most popular and numerous groups of cosmetic products. In chemical terms, they are solutions of surface active agents with the addition of multiple substances such as preservatives, moisturizing agents, fragrances or viscosity modifiers, the aim of which is to improve specific product properties. The present study evaluated the effect of the molecular weight of polyvinylpyrrolidone (PVP) on the properties of face washing products in the form of foam produced with foaming dispensers. A special focus was on key product quality characteristics including foaming properties and skin irritation potential. An addition of PVP to the formulation was found to contribute to an improvement in product foaming properties and a decrease in skin irritation potential. In addition, the studied properties of samples were shown to improve in proportion to the increasing molecular weight of the polymer.

Silicon Image Sensor Technology for in vivo Detection of Surfactant-Induced Corneocyte Swelling and Drying

BACKGROUND

Several instrumental methods can indirectly assess some specific aspects of cutaneous irritation at the level of the stratum corneum (SC).

OBJECTIVE

There is a need for developing more sensitive approaches in this field.

METHODS

We assessed a recently introduced innovative tool (SkinChip) based on capacitive pixel-sensing technology in its potential to detect early discrete manifestations of skin irritation. The sensor generates a detailed non-optical picture corresponding to a capacitance map of the skin surface reaching 50 microm pixel resolution. Some topographical details can be easily disclosed and the SC hydration as well. Two surfactant solutions were tested on volunteers. These solutions were applied under test patches for 2 days on the volar forearms. Clinical and SkinChip assessments were performed 3 h after removing the patch.

RESULTS

The generated images allowed a precise observation of skin irritation which appeared as a two-step process. Early changes consisted of darker pixels corresponding to overhydrated swollen corneocytes at the irritated sites. Two days later, the same area appeared as white pixels, indicating the loss of corneocyte hydration.

CONCLUSION

The SkinChip device appears to be a very sensitive tool for detecting the early steps of surfactant-induced skin irritation affecting the SC.

Interaction of double-chained cationic surfactants, dimethyldialkylammoniums, with erythrocyte membranes: stabilization of the cationic vesicles by phosphatidylcholines with unsaturated fatty acyl chains

We studied the interaction of double-chained cationic surfactants, dimethyldialkylammoniums, (CH3)2N+(CnH2n+1)2, with the lipid bilayer of guinea-pig erythrocytes by observing the haemolysis, aggregation and shape change in the erythrocytes. In the presence of sonicated dispersions of the five dimethyldialkylammoniums tested (n = 10, 12, 14, 16 and 18), haemolysis was induced dose dependently, and at 0.1 mM or higher concentrations, haemolysis was induced more rapidly by dimethyldialkylammoniums with shorter alkyl chains. The cationic surfactants with longer alkyl chains, such as dimethyldipalmitylammonium, induced aggregation of the erythrocytes before haemolysis fully progressed. The vesicles of these long-chain dimethyldialkylammoniums in the presence of phosphatidylcholines with unsaturated fatty acyl chains markedly reduced the haemolysis rates. Furthermore, in the presence of phosphatidylcholines with unsaturated acyl chains the formation of tightly aggregated structures of several erythrocytes was observed. These findings, and analysis by spin label 5-doxylstearic acid, indicate that phosphatidylcholines enriched with unsaturated acyl chains stabilize the cationic vesicles of long-chain dimethyldialkylammoniums and the interaction with the lipid bilayer of erythrocyte membranes as cationic vesicles became prominent.