Annatto-Based Nanoemulsions as Promising Agents for Wound Healing ^†

Introduction: Annatto biocompounds (BiOx) exhibit antioxidant, anti-inflammatory, and antimicrobial properties, which can be enhanced through nanostructuring to promote wound healing. This study aimed to develop and evaluate nanoemulsion formulations. Methodology: Nanoemulsions were prepared by ultrasonication using sunflower oil and/or annatto oil as the oil phase, distilled water as the aqueous phase, and Tween 20 and Span 80 as surfactants. Characterization included hydrodynamic diameter (HD), polydispersity index (PDI), and zeta potential (ZP). Two formulations were obtained: NeBx (nanoemulsions with BiOx extract) and NeOl (nanoemulsions with annatto oil). Biocompatibility and regenerative potential were evaluated in keratinocytes (HaCat) and fibroblasts (FGH) using the MTT assay for viability and the cell migration assay 24 h of treatment with BiOx, Ol (annatto oil), NeBx, and NeOl. Results: NeBx and NeOl exhibited HD of 173 nm and 144 nm, PDI of 0.170 and 0.299, and ZP of −36.2 and −36.53 mV, respectively. Cell viability remained near 100% at concentrations of 31.25, 62.5, and 125 μg/mL for BiOx and NeBx. NeOl also maintained 100% viability, while free Ol was toxic to HaCaT cells, showing only 60% viability at 31.25 μg/mL (p < 0.05) in a dose-dependent manner. Notably, NeBx promoted the greatest cell migration, reaching approximately 80% within 24 h (p < 0.05). Conclusion: Nanostructuring reduced the toxicity of Ol, while NeBx emerged as the most promising formulation for enhancing cell migration, supporting its potential for the development of advanced wound healing therapies.