SODIUM COCOYL ISETHIONATE

To assess the impact of anionic surfactants on the formation of coacervates with cationic guar gum and their subsequent effects on hair care. Coacervates were prepared using ionic precipitation techniques involving four anionic surfactants: sodium lauryl sulfate (SLS), sodium lauroyl sarcosinate (SNL), sodium lauryl sulfoacetate (SLSA), sodium cocoyl isethionate (SCI) and cationic guar gum. Viscosity, spreadability and stickiness sensory analysis were conducted with a panel of volunteers. The coacervates were freeze-dried, and their physicochemical properties were analysed using Raman and Fourier transform infrared spectroscopy, scanning electron microscopy and thermogravimetric analysis. Coacervate formation and stability were dependent on the CGG-to-surfactant ratio, with 0.5% CGG/0.5% surfactant producing the most stable, uniform structures. Spectroscopic analyses confirmed stronger electrostatic and hydrogen bonding interactions at higher CGG concentrations, facilitating greater polymer-surfactant integration. Thermal analysis showed that balanced CGG/surfactant ratios enhanced coacervate stability, while excess surfactant led to lower thermal resistance and weaker deposition. SEM images revealed superior adhesion and homogeneous coverage on damaged hair fibres at 0.5% CGG/0.5% surfactant, suggesting better conditioning effects compared to lower polymer content. The findings emphasize that coacervate stability, deposition efficiency and adhesion to hair fibres are optimized when CGG and surfactants are present in balanced ratios. The 0.5% CGG/0.5% surfactant formulation consistently exhibited superior stability, coverage and interaction with damaged hair, reinforcing its potential as an effective conditioning and protective system. These insights provide a foundation for improving coacervate-based hair care formulations, ensuring enhanced performance and long-term benefits. évaluer l'impact des tensioactifs anioniques sur la formation de coacervats avec la gomme de guar cationique et leurs effets ultérieurs sur les soins capillaires. MÉTHODES: les coacervats ont été préparés à l'aide de techniques de précipitation ionique impliquant quatre tensioactifs anioniques: le laurylsulfate de sodium (SLS), le lauroyl sarcosinate de sodium (SNL), le laurylsulfoacétate de sodium (SLSA) et le cocoyl iséthionate de sodium (SCI), ainsi que de la gomme de guar cationique. On a mené une analyse sensorielle de la viscosité, de l'étalement et de l'adhésivité auprès d'un panel de volontaires. Les coacervats ont été lyophilisés et leurs propriétés physicochimiques analysées par spectroscopie Raman et infrarouge à transformée de Fourier, ainsi qu'avec une microscopie électronique à balayage (MEB) et une analyse thermogravimétrique. RÉSULTATS: la formation et la stabilité du coacervat dépendaient du rapport CGG/tensioactif, avec 0,5% de CGG/0,5% de tensioactif produisant les structures les plus stables et les uniformes. Les analyses spectroscopiques ont confirmé des interactions électrostatiques et hydrogènes plus fortes à des concentrations plus élevées de CGG, facilitant une meilleure intégration du polymère et du tensioactif. L'analyse thermique a montré que des rapports CGG/tensioactif équilibrés amélioraient la stabilité du coacervat, tandis qu'un excès de tensioactif entraînait une résistance thermique plus faible et un dépôt plus léger. Les images de la MEB ont révélé une adhérence supérieure et une couverture homogène sur les fibres capillaires endommagées à 0,5% de CGG/0,5% de tensioactif, ce qui suggère de meilleurs effets revitalisants par rapport à une teneur en polymère plus faible. les résultats soulignent que la stabilit&#xe9

In order to visualize the effects of aqueous surfactant-humectant systems on the skin barrier, an in vitro two-photon fluorescence microscopy (TPM) study, including dual-channel visualization, was carried out. TPM is a non-invasive imaging technique based on two-photon induced nonlinear excitations of fluorophores, with the capability for deep-tissue imaging (up to several hundred micrometers). The following aqueous solutions of surfactants, a humectant, and a surfactant+humectant mixture that contacted pig full-thickness skin (p-FTS) were studied: (i) a harsh surfactant solution-sodium dodecyl sulfate (SDS) (1 wt%); (ii) a harsh surfactant+humectant solution-SDS (1 wt%) + glycerol (10 wt%); (iii) a mild surfactant solution-sodium cocoyl isethionate (SCI) (1 wt%); (iv) a control solution-phosphate-buffered saline (PBS); and (v) a humectant solution-glycerol (10 wt%). Sulforhodamine B (SRB), a hydrophilic fluorescent probe, was used to visualize the effects of aqueous contacting solutions i-v on the skin barrier morphology. The results of the TPM visualization study revealed that SDS induces corneocyte damage by denaturing keratins and creating intracorneocyte penetration pathways. On the other hand, SDS+glycerol did not significantly induce corneocyte damage. The dual-channel TPM images corresponding to aqueous contacting solutions iii-v showed low SRB penetration into the corneocytes, as well as localization of the SRB probe within the lipid bilayers surrounding the corneocytes of the SC. Through a quantification of the amount of SRB that penetrated into the skin as a function of skin depth, we found that adding glycerol to an SDS aqueous contacting solution can significantly reduce the SDS-induced penetration depth of SRB, which provides evidence of the ability of glycerol to mitigate SDS-induced skin barrier perturbation. The distribution of SRB in the p-FTS samples was analyzed using a theoretical model that quantified changes in the skin aqueous pore characteristics induced by aqueous contacting solutions i, ii, iii, and v, relative to aqueous contacting solution iv, the control. The results of the theoretical model indicate the following ranking order in the extent of perturbation to the skin aqueous pores (from the highest to the lowest): i > ii > iii > iv > v. The development of such an in vitro visual ranking methodology, including quantification using TPM, can potentially reduce many costly in vivo screening procedures, thereby significantly reducing the cost and time-to-market of new cosmetic formulations containing surfactants and humectants.

Sodium cocoyl isethionate (SCI) is an important surfactant ingredient in mild, syndet (synthetic detergent) cleansing bars. In vitro and in vivo studies have demonstrated that SCI is mild and less damaging to the skin barrier than soaps and surfactants such as sodium dodecyl sulfate (SDS). We have recently shown that SDS forms small micelles in aqueous solutions contacting the skin relative to the aqueous pores in the stratum corneum (SC), and as a result, the SDS micelles can contribute to SDS skin penetration and induce skin barrier perturbation. In this paper, we attempt to explain the well-documented skin mildness of SCI by examining the size of the SCI micelles relative to that of the aqueous pores in the SC. For this purpose, we have conducted in vitro mannitol skin permeability and average skin electrical resistivity measurements upon exposure of the skin to an aqueous SCI contacting solution in the context of a hindered-transport aqueous porous pathway model of the SC. These in vitro studies demonstrate that an SCI micelle of radius 33.5 +/- 1 Angstrom (as determined using dynamic light-scattering measurements) experiences significant steric hindrance and cannot penetrate into the SC through aqueous pores that have an average radius of 29 +/- 5 Angstrom. We believe that this inability of the SCI micelles to contribute to SCI skin penetration and associated skin barrier perturbation is responsible for the observed skin mildness of SCI. Through in vitro quantitative skin radioactivity assays using (14)C-radiolabeled SCI and pig full-thickness skin (p-FTS), we also show conclusively that SCI skin penetration is dose-independent, an important finding that provides additional evidence that the larger SCI micelles cannot penetrate into the SC through the smaller aqueous pores that exist in the SC, and therefore, cannot induce skin barrier perturbation.

Discrepancies between the one-time patch test and the wash test regarding the ranking of irritancy of detergents have been found in the literature. The aim of the present study was to investigate the concordance of irritancy rank order of 4 anionic detergents tested by 3 different exposure methods, namely one-time occlusive, repeated short-time occlusive and repeated short-time open tests. These detergents were sodium cocoyl isethionate (ISE), sodium lauryl sulfate (SLS), soap and disodium lauryl 3-ethoxysulfosuccinate (SUC). The reactions were evaluated by visual scoring and by transepidermal water loss (TEWL) measurement. When scored visually, the rank order in the one-time test was: SOAP > or = SLS > or = ISE > SUC. The other test methods yielded a different order: SLS > ISE > or = SOAP > SUC. A similar rank order was obtained with TEWL measurement for all exposure methods. Generally, the concordance among the different exposure methods was high when evaluated by TEWL. The concordance was lower when evaluation was performed by visual scoring. The present study demonstrates that the choice of exposure model and evaluation method may be important variables influencing the outcome of irritancy testing. It is proposed that the repeated open test is the best way to simulate most in-use situations where the uncovered skin is exposed to detergents. The repeated occlusive test or the one-time patch test may be better to simulate situations in which the skin is occluded after irritation by detergents.

The majority of adverse skin reactions to personal-care products are presumed to be caused by irritant substances, like surfactants. In this study, different aspects of the irritant reaction after a single exposure to 8 surfactants were characterized during 2 weeks. Solutions of 2% sodium lauryl sulfate, 5% sodium C12-15 pareth sulfate, 5% sodium cocoyl isethionate, 10% disodium laureth sulfosuccinate, 10% sodium cocoamphoacetate, 10% cocamide DEA, 10% cocamidopropyl betaine and 10% lauryl glucoside, respectively, were applied to the forearm of 12 volunteers. Clinical assessment, an evaporimeter, a laser Doppler flowmeter and a corneometer were used for evaluation. The surfactants induced different degrees of irritation. Erythema, transepidermal water loss and skin blood flow exhibited a similar time course, which seemed to be inversely related to the delayed scaling and reduced skin capacitance. The mechanism of the damaging effect of the surfactants seems to be similar, although some minor differences were noted.

The irritant potency of soap (sodium laurate, LAU) as opposed to other anionic detergents is not uniformly agreed upon. The aim of the study was to compare the irritancy of sodium laurate with that of sodium laurylsulphate (SLS), sodium cocoyl isethionate and disodium lauryl 3-ethoxysulphosuc-cinate by means of a 4-day repeated open exposure model in order to achieve a more realistic mimicry of daily practice. The effects of the exposures were evaluated by: a) number of fulfilled exposures, b) visual score after exposures, and c) transepidermal water loss (TEWL) after exposures. In the majority of subjects, exposure to LAU had to be stopped because of burning sensations, erythema and/or scaling. The number of fulfilled exposures to LAU was lower than that of SLS. The other agents were tolerated very well. These less irritative agents had much lower visual scores and TEWL values after the repeated exposures compared with LAU and SLS. The explanation for the irritant nature of LAU in the present study might be the type of alkyl chain length distribution. Its 12-carbon chain content was ≤ 99%, and this agent can therefore be designated as pure sodium laurate. The same holds true for SLS. In daily practice, however, soap is a mixture of different - less irritant - chain lengths. Therefore, these findings cannot be extrapolated to commercially available soap bars.

Synopsis In a cross-over trial two different new syndet bars differing in their content of sodium cocoyl isethionate, disodium lauryl sulfosuccinate and wheat starch as major components were compared in the cleansing of hand skin of 72 healthy volunteers. The preparation designated 'T'containing a higher amount of wheat starch turned out to be less irritant as judged from the parameters itching and erythema (p < 0.05, Wilcoxon's test for matched pairs). The present trial design looks appropriate to differentiate the irritancy potential of two chemically similar syndet bar preparations.

Sodium cocoyl isethionate (SCI) has been a predominant ingredient in syndet bar formulation for more than thirty years. Although cost effective and well recognized for good skin compatibility, SCI is not regularly found in liquid detergent systems due to its limited solubility in water. This study focuses on the understanding of enthalpy of solubilization, equilibrium of solubilization, and the structures and properties of sodium cocoyl isethionate and various surfactants. The purpose of this exercise is to help the formulator to find appropriate surfactant systems to keep sodium cocoyl isethionate in aqueous solution. The solubility of SCI in water is unfavorable in terms of enthalpy of solvation. When setting up equilibrium of solubilization, there are three possible phases, and three methods have been developed to prevent SCI from recrystallizing in aqueous solutions. The first focuses on tying CI ions within micelles made of secondary surfactants. The second focuses on the exchange of sodium ions with ammonium ions (and/or triethanolammonium). The third centers on emulsification of SCI and the subsequent change of micelles into emulsified oil drops. A combination of two or three of these methods will enable the formulator to use SCI as the primary surfactant in liquid detersive systems.