Ulva polysaccharides-based nanoemulsion hydrogel for enhanced skin delivery and protection against UVB-induced damage

Abstract

Ultraviolet (UV)B exposure contributes significantly to skin injury by increasing the generation of reactive oxygen species (ROS), resulting in keratinocyte damage, collagen degradation, inflammation, and premature aging. Current therapeutic approaches are often invasive and associated with undesirable side effects, highlighting the importance of safer, non-invasive alternatives. In this study, a nanoemulsion (NE) was developed using Ulva polysaccharides (UP) as the active ingredient and squalane as a biocompatible oil phase, followed by incorporation into a 0.5% Carbopol hydrogel (NE@hydrogel) for topical application. The NE was prepared via homogenization and ultrasonic treatment, yielding particles with a mean size of 63.8 nm and exhibiting good stability for at least 8 weeks. Skin permeation studies confirmed enhanced dermal delivery, with approximately 21% for hydrophilic and 66% for lipophilic compounds. In vitro, UVB exposure (120 mJ/cm2) lowered HaCaT cell survival with concomitant rise in intracellular ROS, whereas treatment with 10 & times; diluted NE restored cell viability to approximately 74%, reduced ROS levels, and promoted cell migration to 66% at 24 h in the wound healing assay. In vivo, NE@hydrogel application mitigated UVB-induced epidermal thickening from approximately 88 mu m to 50 mu m and preserved epidermal architecture by reducing histological alterations. These results demonstrate that the NE@hydrogel exhibit potent antioxidant and skin-repairing activities, highlighting their potential as natural, non-invasive topical formulations for preventing and alleviating acute UVB-induced skin injury.