PEG-Free Nanoemulsions With Alkyl Polyglucoside and Baccharis dracunculifolia Essential Oil: Physicochemical Behavior, pH Dependence and Skin Repair Properties

Abstract

Alkyl polyglucosides (APG) are biodegradable, non-ionic surfactants from renewable sources with low ecotoxicity. This study developed a novel PEG-free nanoemulsion (NE) using APG to encapsulate Baccharis dracunculifolia essential oil (BDO) for skin repair. Cytotoxicity tests suggested no toxicity for BDO up to 500 μg/mL, and BDO significantly enhanced skin cell migration, indicating potential for skin repair. NEs (1:1 surfactant:BDO) had droplets < 60 nm and low polydispersity (PdI < 0.2). Preliminary NEs had pH > 11, attributed to APG, but adjusting to 6.5 increased droplet size (78 nm) and PdI to 0.3 due to APG interfacial activity changes. After 90 days, NE at pH 6.5 stabilized (~120 nm, PdI < 0.3), indicating a monodisperse system. Conversely, NE at pH 11.5 had a PdI > 0.3 after 21 days, suggesting coalescence. Spectroscopic analyses revealed structural changes in APG and BDO linked to pH variations, supporting the hypothesis of pH-dependent conformational changes in APG. The HET-CAM test indicated a lower irritation score (IS 3.0 ± 0.0) for NE at pH 6.5 vs. 11.5 (IS 3.6 ± 1.15), corroborating the importance of pH adjustment for safe topical applications. This study highlights APG-based NEs as promising for pharmaceuticals and cosmetics, emphasizing the need to further explore APG's pH-sensitive behavior.