SODIUM LAURETH SULFATE

Surfactants are essential in industrial and biological applications, but their interactions with biological systems, particularly skin, often lead to irritation. Understanding the molecular determinants of surfactant-induced skin irritation requires a detailed analysis of the solvation thermodynamics. In this study, we employ all-atom free energy perturbation molecular dynamics (FEP/MD) simulations to investigate the solvation free energy and entropy of sodium lauryl ether sulfate (SLES) surfactants with varying ethoxylate spacer lengths C 12 H 25 (OCH 2 CH 2 ) x OSO 3 Na (where x = 1-3). The solvation free energy is partitioned into van der Waals (vdW) and electrostatic contributions, revealing that (1) vdW interactions become increasingly unfavorable with longer hydrophobic spacers due to entropic penalties for water ordering; (2) electrostatic contributions dominate solvation and grow more favorable with extended ethoxylation, driven by charge delocalization and reduced water structuring around headgroups. Temperature-dependent analyses show that electrostatic solvation entropy becomes less negative with longer spacers, indicating a chaotropic (water-structure-breaking) effect. This trend correlates with experimental observations of a reduced critical micelle concentration (CMC) and attenuated skin irritation, supporting the monomer penetration theory. Our results suggest that electrostatic entropy serves as a predictive descriptor for skin irritation potential, providing a molecular framework for designing milder surfactants. These insights bridge computational thermodynamics with practical applications in personal care and pharmaceutical formulations.

A systematic study on the mechanisms of cleansing artificial skin by solutions of widely used in personal care surfactants disodium laureth sulfosuccinate (DSLSS), sodium laureth sulfate (SLES), sodium dodecyl sulfate (SDS), dodecyl trimethyl ammonium bromide (DTAB), and coco glucoside (CG), is presented. The systematic characterization of soil removal from artificial skin revealed two primary cleansing mechanisms: emulsification and roll-up. Emulsification occurs in systems with very low interfacial tension, such as sebum in SLES solutions, while dimethicone soil was only removed by roll-up. The roll-up effectiveness depends on the surfactant's interfacial activity and its adsorption on the soiled surface. Thus, the strong adsorption of DTAB on the skin leads to dimethicone roll-up at a relatively high interfacial tension of 11 mN/m. The anionic and nonionic surfactants adsorbed less at the artificial skin surface, and the oil/water interfacial tension value lowering below 5 mN/m is necessary for the roll-up to occur. Nonionic CG removed dimethicone at a lower concentration than ionic surfactants. Combining CG with ionic surfactants improved cleaning at lower total concentrations. Surfactant mixtures are used to formulate simple cleansing formulations, whose performance is also investigated by the developed in vitro approach. The results obtained allow for a good rating of the formulations, which correlates well with the performance of the surfactant mixtures and their interfacial activity.

Ex vivo penetration tests are important tools in cosmetic and pharmaceutical research. However, variability of experimental setups is challenging when reviewing literature. Different skin models, pre-treatments and experimental parameters render comparison difficult. Thus, our aim was to conduct ex vivo penetration tests using caffeine in different setups with varying incubation conditions (ambient vs. Franz cells, infinite vs. finite dose). Additionally, the impact of skin pre-treatment with different aggressors (surfactants, UVA irradiation) should be considered. Possible synergistic barrier damage of surfactants and UVA irradiation should be explored. Analysis was conducted using quantitative confocal Raman spectroscopy. Results showed that incubation time and extensive hydration (20 h in Franz cells) had the greatest impact on penetration behavior. Additional irradiation after pre-treatment with oil-in-water nanoemulsions showed no strong impact on caffeine penetration in general, irrespective of surfactant type. However, in case of sodium lauryl ether sulfate, a trend towards enhanced values was observed due to irradiation (1.3-fold). This suggests cumulative skin barrier damage of irritant surfactants and UVA irradiation, potentially due to stratum corneum alterations. Further studies using different irradiation regimens are planned to confirm this hypothesis.

The safety assessment of cosmetics considers the exposure of a 'common consumer', not the occupational exposure of hairdressers. This review aims to compile and appraise evidence regarding the skin toxicity of cysteamine hydrochloride (cysteamine HCl; CAS no. 156-57-0), polyvinylpyrrolidone (PVP; CAS no. 9003-39-8), PVP copolymers (CAS no. 28211-18-9), sodium laureth sulfate (SLES; CAS no. 9004-82-4), cocamide diethanolamine (cocamide DEA; CAS no. 68603-42-9), and cocamidopropyl betaine (CAPB; CAS no. 61789-40-0). A total of 298 articles were identified, of which 70 were included. Meta-analysis revealed that hairdressers have a 1.7-fold increased risk of developing a contact allergy to CAPB compared to controls who are not hairdressers. Hairdressers might have a higher risk of acquiring quantum sensitization against cysteamine HCl compared to a consumer because of their job responsibilities. Regarding cocamide DEA, the irritant potential of this surfactant should not be overlooked. Original articles for PVP, PVP copolymers, and SLES are lacking. This systematic review indicates that the current standards do not effectively address the occupational risks associated with hairdressers' usage of hair cosmetics. The considerable irritant and/or allergenic potential of substances used in hair cosmetics should prompt a reassessment of current risk assessment practices.

The main objective of this paper is to analyse the composition of a sulphate-free binary or ternary surfactant system with alkyl olefin sulfonate (AOS), alkyl polyglucoside (APG) and lauryl hydroxysultaine (Sultaine). The composition was optimized by observing critical parameters such as surface activity and rheological properties while varying the concentration of APG in a ternary system, varying the ratio of AOS and Sultaine in a binary system and studying the effect of sodium chloride addition. The experimental results can provide an alternative, sulphate-free surfactant system to replace the common system containing sodium laureth sulfate (SLES) and cocamidopropyl betaine (CapB), without compromising on the parameters previously mentioned. A DuNouy Ring was utilized on a tensiometer to measure the surface tension of the samples. To observe foaming abilities of samples, a visual foaming study was conducted and recorded by taking pictures. A TA instruments mechanical rheometer was used to measure the viscosity. Studying the effect of APG concentration on surface tension illustrated that as APG concentration decreases, surface tension decreases as well. The minimum surface tension was found to be 26.587 for 7.5 wt.% AOS and 7.5 wt.% Sultaine. When the ratio between AOS and Sultaine changed, the 1:1 system produced the lowest surface tension value again. As the concentration of AOS decreased in the ratio, the surface tension increased. When the ratio was held constant, and APG was introduced into the system, the systems containing APG had higher surface tension values compared with the systems with the same ratios but did not have APG added. As the concentration of salt increased, the surface tension decreased for AOS, increased for the binary mixture and had no effect on Sultaine. Foaming has a direct correlation with surface tension so a decrease in surface tension led to better foaming abilities; therefore, the 1:1 ratio of AOS:Sultaine had the best foaming qualities. The AOS/Sultaine system exhibited Maxwellian behaviour, suggesting the presence of worm-like micellar structures. As the concentration of APG increased, the viscosity decreased and at a concentration of 2.5 wt.% AOS, 5 wt.% APG and 7.5 wt.% Sultaine, the system changed from shear thinning non-Newtonian fluid to Newtonian. Varying the ratio of AOS:Sultaine in the binary system, showed as the ratio changed, the viscosity decreased, and at a ratio of 1:3 AOS:Sultaine, the system was primarily Newtonian. As the ratio remained constant and APG was added, the viscosity continued to decrease and the 1:3 ratio was completely Newtonian. The addition of salt had no effect on the viscosity of Sultaine, but the viscosity of AOS increased at a salt concentration of 2 wt.%. The binary mixture saw as the concentration of salt increased, the viscosity profile decreased, even though the system remained non-Newtonian and shear thinning. The surface activity and rheological study of the sulfate-free surfactant systems unveil a strong synergistic interaction between AOS and Sultaine specifically at a ratio of 1:1 resulting in high surface activity and corresponding good foaming and formation of entangled wormlike micelles resulting in excellent viscosity build in the system. If introducing a biobased surfactant into this system is desired without completely compromising the performance properties, the ternary surfactant system 4.5 wt.% AOS, 3 wt.% APG and 7.5 wt.% Sultaine should be considered optimal. Any further addition of APG or changing the ratio results in detrimental reductions of all performance controlling physio-chemical parameters. OBJECTIF: l’objectif principal de cet article est d’analyser la composition d’un système de surfactant binaire ou ternaire sans sulfate utilisant l’alkyle sulfonate oléfine (alkyl olefin sulfonate, AOS), l’alkyle polyglucoside (APG) et le lauryl hy

Our skin is continuously exposed to different amphiphilic substances capable of interaction with its lipids and proteins. We describe the effect of a saponin-rich soapwort extract and of four commonly employed synthetic surfactants: sodium lauryl sulfate (SLS), sodium laureth sulfate (SLES), ammonium lauryl sulfate (ALS), cocamidopropyl betaine (CAPB) on different human skin models. Two human skin cell lines were employed: normal keratinocytes (HaCaT) and human melanoma cells (A375). The liposomes consisting of a dipalmitoylphosphatidylcholine/cholesterol mixture in a molar ratio of 7:3, mimicking the cell membrane of keratinocytes and melanoma cells were employed as the second model. Using dynamic light scattering (DLS), the particle size distribution of liposomes was analyzed before and after contact with the tested (bio)surfactants. The results, supplemented by the protein solubilization tests (albumin denaturation test, zein test) and oil emulsification capacity (using olive oil and engine oil), showed that the soapwort extract affects the skin models to a clearly different extent than any of the tested synthetic surfactants. Its protein and lipid solubilizing potential are much smaller than for the three anionic surfactants (SLS, ALS, SLES). In terms of protein solubilization potential, the soapwort extract is comparable to CAPB, which, however, is much harsher to lipids.

The method of colloid titration with poly(diallyldimethylammonium) chloride has been improved to detect the endpoint with an off-vessel light reflectance sensor. The digital color sensor used measures light reflectance by means of light guides, with no immersion into the reaction solution. In such a method, the optical signal is free of disturbances caused by sticky flocs in the solution. The improved automatic titration set was applied for the determination of sodium laureth sulfate (SLES) in industrial batches and commercial personal care products. The sample color and opacity do not disturb the SLES quantification. When the SLES content lies in the range from 5% to 9%, the optimal sample weight is from 6 g to 3 g.

Preservatives are primarily used for their antimicrobial properties and form an important component of food, cosmetic, and drug formulations. The efficacy of preservatives depends on various factors, which include the bacterial membrane composition and the interaction between components of a specific formulation. Molecules such as phenoxyethanol (POE), caprylylglycol (CPG), and methylparaben (MEP) are widely used as preservatives in the food and cosmetic industries; however, a molecular understanding of their interactions with surfactants and the kinetics of membrane partitioning remains unexplored. In this study, coarse-grained molecular dynamics simulations were carried out to evaluate and quantify the kinetics of membrane partitioning for preservatives and surfactants in the Escherichia coli inner phospholipid membrane. We propose a mass-transfer-based model to determine membrane partitioning kinetics. Faster kinetics were observed for first-order partitioning of POE and MEP (τ ∼ 0.01 μs) when compared with zeroth-order kinetics (τ ∼ 0.1 μs) for CPG. In contrast, surfactants such as sodium laureth sulfate (SLES) and cocamidopropyl betaine (CAPB) follow zeroth-order membrane partitioning kinetics with significantly higher time constants (1.5-10 μs). Interestingly, zeroth-order kinetics occurred when micellar aggregates were present, and the rate-controlling step was the slow rate of release of single molecules from the aggregate, in comparison to faster membrane uptake kinetics. Using a sequential micellar breakup model with single surfactant release dynamics, we analytically recover this unique zeroth-order membrane partitioning kinetics. In preservative-surfactant mixtures, the kinetics of preservative partitioning were found to decrease by a factor of 2-10. Significantly, the equilibrium membrane saturation coefficients for both preservatives and surfactant remained invariant in the mixtures due to the wide separation of partitioning time scales for the surfactants and preservatives. The kinetic models developed in this study can be used to quantify membrane partitioning of preservatives and understand the influence of surfactants in specific formulations.

Given the underdevelopment and sensitivity of babies' eyes, frequently used baby bath products have garnered attention for their ocular irritation safety. The selection and application of raw materials are key factors. We tested 39 commercial baby bath products for ocular irritation safety and proposed a novel evaluation method using the "Risk Attention Index" to analyze formulation risk factors. The ocular irritation potential of 39 commonly used raw materials under typical usage conditions was investigated via animal and cell models. Results showed over 20% of commercial products had safety risks. Surfactants like cocamidopropyl betaine (CAPB), sodium laureth sulfate (SLES), and sodium lauroamphoacetate (SLA) had the highest "Risk Attention Index", requiring special attention. Some fragrance components were also potential irritants. Combining SLES with panthenol, maltooligosyl glucoside/hydrogenated starch hydrolysate, and Tween ® -28 could significantly reduce its irritation in an animal model. The same ingredients from different sources led to inconsistent irritation results. This suggests that manufacturing processes of raw materials, in addition to their chemical properties, concentration, and combination methods, all influence the ocular irritation potential. This study provides key scientific evidence for assessing ocular irritation and developing low-irritation formulations in baby bath products, thereby enhancing product safety.

Natural biopolymers become increasingly attractive as bio-based alternatives to petrol-based rheological modifiers, especially in personal care applications. However, many polysaccharides exhibit undesired properties in cosmetic applications such as limited viscosifying characteristics, unpleasant sensory properties, or incompatibility with certain formulation compounds. Here, a comprehensive rheological analysis of non-decorated acetan-like heteroexopolysaccharides derived from two Kozakia baliensis strains was performed in selected surfactant formulations. The results were compared to native xanthan gum and a genetically engineered xanthan variant, Xan∆gumFGL, which lacks any acetyl- and pyruvyl moieties and whose rheological properties are unaffected by saline environments. All four polysaccharides displayed a highly similar rheological performance in the non-ionic surfactant lauryl glucoside, while the rheological properties differed in amphoteric and anionic surfactants cocamidopropyl betaine and sodium laureth sulfate due to minor changes in side chain composition. Polysaccharide precipitation was observed in the presence of the cationic surfactant. Nevertheless, the native heteroexopolysaccharide derived from K. baliensis LMG 27018 shows significant potential as a salt-independent rheological modifier compared to the genetically engineered Xan∆gumFGL variant. In addition, blends of heteroexopolysaccharides from K. baliensis and several galactomannans displayed synergistic effects which were comparable to native xanthan gum-galactomannan blends. This study shows that heteroexopolysaccharides of K. baliensis are capable of further extending the portfolio of bio-based rheological modifiers.

As the global surfactant market continues to expand, there is an increasing need to develop bio-based alternatives in the shift towards a circular economy. This study focuses on the synthesis of polar, amphoteric, amine-oxide surfactants starting from biomass-derived monosaccharides and demonstrating their potential in various applications. The synthesis involved a reductive amination of the sugars with an alkylamine and formaldehyde followed by oxidation to produce N-oxide surfactants. These bio-based surfactants exhibited promising properties, including high solubility, foamability, surface tension reduction, and critical micelle concentration. In particular, N-GalA1.10 and N-GalA1.12 showed comparable performance to commercial surfactants. Furthermore, these bio-based surfactants demonstrated significantly lower skin irritation potential when compared to petrochemical-derived counterparts like sodium laureth sulfate (SLES), making them potentially suitable for personal care products. The biodegradability assessment revealed that N-GalA1.12 exhibited good biodegradation, indicating its potential environmental compatibility. In conclusion, this study highlights the potential of bio-based N-oxide surfactants derived from monosaccharides as sustainable and skin-friendly alternatives to traditional amphoteric surfactants, like cocamidopropyl betaine (CAPB).

We present a new liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for simultaneous determination of sodium lauryl sulfate and sodium laureth sulfate homologues in the range of alkyl chain length C 12 -C 16 with 0-5 ethoxy groups. The method is based on scanning the precursor ions fragmenting to m/z 80 and 97 (Precursor Ion Scanning mode), which makes it specific for species with easily cleavable sulfate groups. By monitoring fragmentation of thus discovered quasi-molecular ions we were able to unequivocally identify all sulfate species present in complex mixtures of alkyl and alkyl-ether sulfates with molecular weight ranging from 200 to 600 m/z. Because of the intrinsic sulfate-sensitivity, the presented method can be also applied to non-sodium salts of alkyl- and alkyl-ether sulfates (e.g. ammonium, mono- or triethanolamine, etc.), which are often used by cosmetic manufacturers to justify the misleading SLS- and SLES-free claims (where SLS and SLES refer to sodium lauryl sulfate and sodium laureth sulfate, respectively). The use of reversed phase liquid chromatography (RPLC) column with C4 instead of C18 shortened significantly the overall analysis time and allowed us to use a semiquantitative method (based on single standard for Quantitative Analysis of Multi-component System, QAMS) to determine several SLS and SLES homologues in one run with the limit of quantification (LOQ) = 0.4 µg/mL and of detection (LOD) in the range 0.12-0.97 µg/mL. The method was successfully applied to 17 commercially available cosmetic/household products allowing verification of their manufacturers' declarations.