High-Load Amino Acid Nanoemulsion: Physicochemical Optimization and Dermal Bioactivity

Amino acids such as GABA, glycine, and proline play critical roles in extracellular matrix renewal, but their high hydrophilicity limits dermal delivery. This study aimed to develop a stable oil-in-water nanoemulsion capable of incorporating a high amino acid load (20% w/w) and to evaluate its biological activity. Nanoemulsions were prepared using high-pressure homogenization at varying surfactant concentrations (5-7% w/w) and pressures (80-120 MPa). Physicochemical properties, stability, and amino acid content were evaluated, and biological activity was assessed in fibroblasts. The selected formulation (5% surfactant, 120 MPa), identified based on a balance of droplet size, stability, and biological response, showed improved stability and retained >95% of actives over 12 weeks. It significantly enhanced collagen and elastin gene expression. These findings demonstrate that process optimization enables stable high-load amino acid nanoemulsions with potential applications in dermal delivery.