Skin hydration as a tool to control the distribution and molecular effects of intermediate polarity compounds in intact stratum corneum

Effect of intermediate polarity molecule on phase transitions and bilayer structure in phospholipid membranes

Lipid-based formulations are widely utilized in various applications including food, cosmetics, and pharmaceuticals. The properties of these formulations can be influenced by changes in the external environment. As one example, dehydration can induce phase changes and alter the structural organization and molecular dynamic in the formulation, which potentially compromises the reversibility to a dispersed liquid crystalline state upon rehydration. A common strategy to prevent phase transitions and mitigate these effects involves the addition of small molecules with low vapor pressure. The protective effects of such additives will depend on their distribution within the lipid self-assembly structure. In this study, we investigate the effects of an intermediate polarity compound on phospholipid self-assembly in varying hydration conditions. As a model intermediate polarity compound, we use 1,2,3-trimethoxy propane (TMP), and we compare its effects with hydrophobic and hydrophilic compounds of similar molecular weight on the same lipid system. Lipid self-assembly structure and molecular dynamics were characterized using a multi-technique approach, including solid-state NMR, differential scanning calorimetry, and small- and wide-angle X-ray scattering. It is demonstrated that TMP influences lipid self-assembly at low water content while its effect becomes negligible at high water content. The observations can be rationalised based on the partitioning of TMP within the lamellar structure, where it behaves as a hydrophobic additive in dry conditions and as a hydrophilic additive in more hydrated conditions. The underlying principles of TMP's dual behavior highlight the potential of other intermediate polarity molecules in tailoring the properties of lipid-based formulations.

Physicochemical and Sensory Evaluation of Sustainable Plant-Based Homopolymers as an Alternative to Traditional Emollients in Topical Emulsions

Objectives: This study evaluated the potential of sustainably sourced, plant-based homopolymers derived from citronellol as an alternative to the traditional emollients used in pharmaceutical, cosmetic, and personal care products. With increasing emphasis on environmentally friendly ingredients and manufacturing processes, this study assessed the efficacy of these homopolymers in semi-solid and emulsion-based formulations. Methods: The analyses focused on physicochemical, sensory, biophysical, and neurosensory characteristics. Results: The results demonstrated that emulsions containing sustainable homopolymers maintained viscoelastic stability, preserving rheological properties over time under varying conditions. These formulations showed comparable structural and functional stability to those with traditional emollients while offering skin hydration, moisture retention, and elasticity, with reduced transepidermal water loss. Sensory evaluations highlighted positive user acceptance, with participants favoring the skin feel and in-use qualities of these emulsions over synthetic alternatives. Neurosensory analyses confirmed the strong visual appeal of the product packaging, capturing user attention effectively. Conclusions: These findings underline the capability of plant-based homopolymers to replace traditional emollients while providing significant consumer appeal and sustainability benefits. This study establishes their potential as viable components in the development of more eco-friendly topical formulations for the pharmaceutical, cosmetic, and personal care industries.

Cryogenic probe technology enables multidimensional solid-state NMR of the stratum corneum without isotope labeling

Solid-state NMR has great potential for investigating molecular structure, dynamics, and organization of the stratum corneum, the outer 10-20 μm of the skin, but is hampered by the unfeasibility of isotope labelling as generally required to reach sufficient signal-to-noise ratio for the more informative multidimensional NMR techniques. In this preliminary study of pig stratum corneum at 35 °C and water-free conditions, we demonstrate that cryogenic probe technology offers sufficient signal boost to observe previously undetectable minor resonances that can be uniquely assigned to fluid cholesterol, ceramides, and triacylglycerols, as well as enables 1H-1H spin diffusion monitored by 2D 1H-13C HETCOR to estimate 1-100 nm distances between specific atomic sites on proteins and lipids. The new capabilities open up for future multidimensional solid-state NMR studies to answer long-standing questions about partitioning of additives, such as pharmaceutically active substances, between solid and liquid domains within the protein and lipid phases in the stratum corneum and the lipids of the sebum.

Antiaging in a Bottle: Bioactive Competency of Plasma-Generated Nitric Oxide Water for Modulation of Aging-Related Signature in Human Dermal Cells

Nitric oxide (NO), a potential therapeutic antiaging molecule, modulates various physiological and cellular processes. However, alterations in endogenous NO levels brought on by aging impact multiple organ systems and heighten susceptibility to age-related skin diseases. This correlation underscores the importance of investigating NO-based antiaging interventions. Nonthermal plasma-generated NO is a promising avenue for cosmetic and regenerative medicine due to its capacity to stimulate cellular growth. Herein, we examine the potential of plasma-generated nitric oxide water (NOW) as a bioactive agent in human dermal fibroblasts, emphasizing gene expression patterns linked to extracellular matrix (ECM) breakdown and cellular senescence. The findings of our study indicate that administering NOW at lower dosages enhances cell migration and proliferation. Moreover, the genetic signatures associated with ECM synthesis, antioxidant defense, and antisenescence pathways have been analyzed in NOW-exposed cells. Notably, the downregulation of ECM-degrading enzyme transcripts─collagenase, elastase, and hyaluronidase─suggests NOW's potential in mitigating the intrinsic skin aging phenomena, emphasizing the promise of NO-based interventions in advancing antiaging strategies within regenerative medicine.

Skin-Inspired All-Natural Biogel for Bioadhesive Interface

Natural material-based hydrogels are considered ideal candidates for constructing robust bio-interfaces due to their environmentally sustainable nature and biocompatibility. However, these hydrogels often encounter limitations such as weak mechanical strength, low water resistance, and poor ionic conductivity. Here, inspired by the role of natural moisturizing factor (NMF) in skin, a straightforward yet versatile strategy is proposed for fabricating all-natural ionic biogels that exhibit high resilience, ionic conductivity, resistance to dehydration, and complete degradability, without necessitating any chemical modification. A well-balanced combination of gelatin and sodium pyrrolidone carboxylic acid (an NMF compound) gives rise to a significant enhancement in the mechanical strength, ionic conductivity, and water retention capacity of the biogel compared to pure gelatin hydrogel. The biogel manifests temperature-controlled reversible fluid-gel transition properties attributed to the triple-helix junctions of gelatin, which enables in situ gelation on diverse substrates, thereby ensuring conformal contact and dynamic compliance with curved surfaces. Due to its salutary properties, the biogel can serve as an effective and biocompatible interface for high-quality and long-term electrophysiological signal recording. These findings provide a general and scalable approach for designing natural material-based hydrogels with tailored functionalities to meet diverse application needs.

Solubility of Foreign Molecules in Stratum Corneum Brick and Mortar Structure

The barrier function of the skin is mainly assured by its outermost layer, stratum corneum (SC). One key aspect in predicting dermal drug delivery and in safety assessment of skin exposure to chemicals is the need to determine the amount of chemical that is taken up into the SC. We here present a strategy that allows for direct measures of the amount of various solid chemicals that can be dissolved in the SC in any environmental relative humidity (RH). A main advantage of the presented method is that it distinguishes between molecules that are dissolved within the SC and molecules that are not dissolved but might be present at, for example, the skin surface. In addition, the method allows for studies of uptake of hydrophobic chemicals without the need to use organic solvents. The strategy relies on the differences in the molecular properties of the added molecules in the dissolved and the excess states, employing detection methods that act as a dynamic filter to spot only one of the fractions, either the dissolved molecules or the excess solid molecules. By measuring the solubility in SC and delipidized SC at the same RHs, the same method can be used to estimate the distribution of the added chemical between the extracellular lipids and corneocytes at different hydration conditions. The solubility in porcine SC is shown to vary with hydration, which has implications for the molecular uptake and transport across the skin. The findings highlight the importance of assessing the chemical uptake at hydration conditions relevant to the specific applications. The methodology presented in this study can also be generalized to study the solubility and partitioning of chemicals in other heterogeneous materials with complex composition and structure.