Evaluation of anionic surfactants effects on the skin barrier function based on skin permeability

Dermal bioavailability of perfluoroalkyl substances using in vitro 3D human skin equivalent models

Perfluoroalkyl substances (PFAS) have been identified in various products that come in contact with human skin, ranging from school uniforms to personal care products. Despite this, knowledge on human dermal uptake of PFAS is lacking. Thus, the human dermal absorption of 17 PFAS was assessed, for the first time, using in vitro 3D-human skin equivalent models exposed to 500 ng/cm2 PFAS dissolved in methanol over 24-36 h. The distribution of target PFAS is presented, based on three fractions: absorbed, un-absorbed, and retained within skin tissue (absorbable dose). Perfluoropentanoic acid (PFPeA) and perfluorobutane sulfonate (PFBS) had the highest absorbed fraction, 58.9 % and 48.7 % respectively, with the absorbed fraction decreasing with increasing carbon chain length of the studied perfluorocarboxylic acids (PFCAs) (r = 0.97, p = 0.001) and perfluorosulfonic acids (PFSAs) (r = 0.97, p = 0.004). Interestingly, while longer chain PFAS (Cn ≥ 9) were not directly absorbed, a large fraction of the exposure dose was detected within the skin tissue at the end of the exposure. This was most apparent for perfluoroundecanoic acid (PFUnDA) and perfluorononane sulfonate (PFNS) for which 66.5 % and 68.3 % of the exposure dose was found within the skin tissue, while neither compound was detected in the absorbed fraction. For compounds with a carbon chain length > 11, the fraction found within the skin tissue, decreases with increasing chain length. Physicochemical properties played a role in dermal permeation of PFAS, with a clear inverse correlation between logKOW and absorbed fraction for both PFCAs (r = -0.97; p ≤ 0.001) and PFSAs (r = -0.99; p ≤ 0.001). Steady-state flux (JSS) and permeation coefficients (Papp) were determined for target compounds with significant permeation after 36 h exposure (C5-C8 PFCAs and C4-C7 PFSAs). In general, both the flux and permeation coefficient decreased with increasing chain length.

Effects of ultra-pure soft water on the hands of nurses in a neonatal intensive care unit: A randomized crossover study

BACKGROUND

Healthcare workers (HCWs) wash their hands with tap water (TW) and soap. However, hard TW causes dermatitis.

OBJECTIVES

The present study aimed to compare the effects of ultra-pure soft water (UPSW) with those of TW on the hands of HWCs.

METHODS

The present study was a prospective randomized trial with a crossover design. All the nurses in the neonatal intensive care unit (NICU) at the study centre were divided into Sequence 1 (UPSW to TW) or 2 (TW to UPSW) and washed their hands with TW or UPSW in alternating 4-week periods with a 4-week washout period. Trans-epidermal water loss (TEWL) and stratum corneum hydration (SCH) were evaluated. Skin condition was self-assessed.

RESULTS

Twenty-one and 22 nurses were assigned to Sequence 1 and Sequence 2, respectively. USPW increased SCH to a significantly greater degree than TW (mean: 26.3 μS ± 12.3 SD; 95% confidence interval: 1.12-51.54; p = 0.041) although it did not affect TEWL. UPSW use significantly improved the subjects' skin condition, as reflected in an overall increase in the assessment scores.

CONCLUSIONS

UPSW improved SCH and the condition of hand skin. Prolonged USPW use may increase nurses' comfort during work and hand hygiene compliance.

An exploratory study of the effects of the pH of synthetic urine on skin integrity in healthy participants

Background: Incontinence-associated dermatitis (IAD) develops from prolonged exposure of skin to urine and/or stool and represents a common complication in older adults, reducing the quality of life. Increased pH is an important etiologic factor of IAD, however, the relationship between urinary pH and skin barrier disruption remains unclear. Objective: To examine the effects of synthetic urine (s-urine) at various pH on transepidermal water loss (TEWL), stratum corneum hydration (SCH) and skin surface pH. Methods: S-urine solutions (pH 5.0-9.0) were applied to the volar forearms of 15 healthy participants for 2 hrs, with another site serving as the untreated control. Measurements of TEWL, SCH and skin surface pH were obtained at baseline and after each challenge. Skin buffering capacity was also examined in 5 volunteers by recording skin pH at baseline, after 2 hrs exposure and every 5 mins for 40 mins. Results: TEWL and SCH were increased following exposure to s-urine compared to baseline values. Although there was tendency for pH to an increase after exposure, further investigation showed that changes are only temporal as pH value is restored to baseline within 5 mins. There were no significant differences between solutions. Conclusions: This study revealed that urine disrupts healthy skin integrity; however, its effects are not pH dependent. Transient changes were observed on the acid mantle of the skin due to its innate buffering capacity. Future studies need to examine the effects of urine combined with bacteria responsible for pH elevation in patients with urinary incontinence.

Transdermal Delivery of Therapeutic Compounds With Nanotechnological Approaches in Psoriasis

Psoriasis is a chronic, immune-mediated skin disorder involving hyperproliferation of the keratinocytes in the epidermis. As complex as its pathophysiology, the optimal treatment for psoriasis remains unsatisfactorily addressed. Though systemic administration of biological agents has made an impressive stride in moderate-to-severe psoriasis, a considerable portion of psoriatic conditions were left unresolved, mainly due to adverse effects from systemic drug administration or insufficient drug delivery across a highly packed stratum corneum via topical therapies. Along with the advances in nanotechnologies, the incorporation of nanomaterials as topical drug carriers opens an obvious prospect for the development of antipsoriatic topicals. Hence, this review aims to distinguish the benefits and weaknesses of individual nanostructures when applied as topical antipsoriatics in preclinical psoriatic models. In view of specific features of each nanostructure, we propose that a proper combination of distinctive nanomaterials according to the physicochemical properties of loaded drugs and clinical features of psoriatic patients is becoming a promising option that potentially drives the translation of nanomaterials from bench to bedside with improved transdermal drug delivery and consequently therapeutic effects.

A Data-Mining Approach for the Quantitative Assessment of Physicochemical Properties of Molecular Compounds in the Skin Flux

This paper aimed to provide an insight into the mechanism of transdermal penetration of drug molecules with respect to their physicochemical properties, such as solubility (S), the presence of enantiomer (ET) and logarithm of octanol-water partition coefficient (log P), molecular weight (MW), and melting point (MP). Propionic acid derivatives were evaluated for their flux through full-thickness skin excised from hairless mice upon being delivered from silicone-based pressure-sensitive adhesive (PSA) matrices in the presence or absence of various enhancers. The skin fluxes of model compounds were calculated based on the data obtained using the method engaged with the diffusion cell system. The statistical design of experiments (DoE) based on the factorial approach was used to find variables that have a significant impact on the outcomes. For the prediction of skin flux, a quantitative equation was derived using the data-mining approach on the relationship between skin permeation of model compounds (~125 mg/ml) and involved physicochemical variables. The most influential variables for the skin flux of propionic acid derivatives were the melting point (0.97) followed by the presence of enantiomer (0.95), molecular mass (0.93), log P values (0.86), and aqueous solubility (0.80). It was concluded that the skin flux of molecular compounds can be predicted based on the relationship between their physicochemical properties and the interaction with cofactors including additives and enhancers in the vehicles.

The involvement of protein denaturing activity in the effect of surfactants on skin barrier function

BACKGROUND/PURPOSE

Detailed information on the mechanism by which surfactants affect the skin barrier function is still scarce. We investigated the contribution of protein denaturation to the effect of surfactants on barrier function.

METHODS

The Transmission Index method, which evaluates the actual effect of surfactants on barrier function, was combined with a microplate assay measuring protein denaturation activity. The correlation between the TI value and the reciprocal of the median effect concentration (1/EC50) was analyzed for 19 surfactants. The contribution of protein denaturation to the effect of surfactants was discussed based on the 1/EC50 per TI value.

RESULTS

A few surfactants showed high TI value. Nonionic surfactants had no effect. The EC50 varied without certain trend. For amino acid-based surfactants, there was a gradual inverse correlation between the TI value and the 1/EC50.

CONCLUSION

The difference in the alkyl structure and the ion source affected the skin barrier function. Protein denaturing activity of the surfactant was not a critical factor. This suggests that the effect on intercellular lipids was the major factor. However, the magnitude of the contribution of protein denaturation activity varied depending on the surfactant, suggesting that each surfactant has a different mechanism of influence on skin barrier function.

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.

Amino-Acid Surfactants in Personal Cleansing (Review)

The consumer demand for greener, sustainable and skin friendly chemicals is driving the use of amino-acid based surfactants in the personal care area. Acyl glutamates and glycinates are already being used in commercial products. Available literature clearly shows that the amino acid based surfactants are generally milder than their corresponding alkyl sulfates and carboxylates. However, they do offer some interesting challenges in the area of structuring and consumer desired lather properties. Furthermore, the amino acid surfactants, unlike alkyl sulfates, have pH as an interesting variable for fine-tuning their functional properties. In this paper, the solution, interfacial and skin mildness properties of commercially relevant amino acid surfactants are reviewed and the opportunities and challenges for their wider application are outlined.