Ethosomal Nanocarriers for Hydrophilic Peptide Encapsulation: Formulation Optimization, Stability, and In Vitro Release Performance

Abstract

Background: Hydrolyzed collagen peptides (HCP) are widely used as bioactive ingredients in anti-aging and skin rejuvenation formulations due to their role in supporting skin hydration, elasticity, and extracellular matrix integrity. However, their high hydrophilicity limits effective incorporation into lipid-based systems, and restricts controlled release from formulations. Objective: In this study, ethosomal nanocarriers were designed as a phospholipid-ethanol-based system to promote favorable molecular interactions with hydrophilic peptides, aiming to enhance the encapsulation, stability, and controlled release of HCP for dermocosmetic applications. Methods: HCP-loaded ethosomes were prepared using phospholipid (Lipoid P75) and ethanol and optimized by varying high-pressure homogenization cycles. Physicochemical properties, including vesicle size, distribution uniformity, zeta potential, pH, and long-term stability, were monitored for up to 180 days. Vesicle morphology and peptide-lipid interactions were characterized using cryo-scanning electron microscopy and FTIR spectroscopy. Encapsulation efficiency was determined by ultrafiltration, while cytocompatibility was assessed in HaCaT keratinocyte cells. In vitro release behavior was investigated using Franz diffusion cells and compared with aqueous HCP solutions. Results: All formulations exhibited nanoscale size distribution and high colloidal stability, with negative zeta potentials ranging from -42.9 to -76.7 mV. The optimized formulation demonstrated sustained encapsulation efficiency (73% after 180 days) and preservation of peptide structure, as confirmed by FTIR, indicating effective chemical stabilization within the ethosomal matrix. Cytotoxicity studies confirmed good skin cell compatibility. In vitro release studies revealed a controlled and prolonged release profile from ethosomal carriers compared with free HCP solutions, suggesting improved topical bioavailability of collagen peptides. Conclusions: To the best of our knowledge, this work provides one of the first systematic investigations of optimized ethosomal systems for the stabilization of hydrophilic collagen peptides as anti-aging dermocosmetic ingredients. These findings demonstrate that optimized HCP-loaded ethosomes represent a promising ingredient formulation platform enabling bioactive preservation, formulation stability, and controlled topical performance for collagen-based skin rejuvenation applications.