Polymeric nanogels loaded with <i>Eugenia uniflora</i> L. dry extract: the role of span ^® 80 in rheology, release, and skin permeation

Fungal skin infections remain a global health concern, and current topical treatments often present limitations in efficacy and skin permeation, highlighting the need for innovative actives and delivery systems. <i>Eugenia uniflora</i> L. (EU) has demonstrated antifungal activity. Therefore, this study aimed to develop and characterize nanogels containing poloxamers and Span 80 for the topical delivery of EU dry extract (DryExt). An analytical method was developed, and formulations were obtained with 3, 6, and 12% of Span 80 (PS3%, PS6%, and PS12%, respectively) with DryExt. The formulations were fully characterized, and rheological, <i>in vitro</i> release, permeation, and irritation potential studies were performed. The formulations had nanometric diameters (200-400 nm), spherical, with a dark and thick halo, suggesting vesicle formation. With increasing Span 80 concentration, the viscosity of the formulations increased, and the sol-gel transition temperature decreased. Span 80 also enhanced the release and permeation of DryExt markers (ellagic acid - EA, gallic acid - GA, myricitrin - MYR). For instance, compared with PS3%-DryExt, PS12%-DryExt enhanced GA and MYR skin permeation by up to 5-fold. No irritation was observed. In conclusion, adding Span to the formulation benefits skin permeation and viscosity, supporting its potential as an effective topical antifungal delivery system.