Amphiphilic Cationic Xanthan Gum: A Versatile Excipient for Fusidic Acid Microemulgel Formulations

A cationic derivative of xanthan gum (Ca-XG) was synthesized through grafting of quaternary amine groups, with a degree of substitution of 0.43 confirmed by ¹H-NMR analysis. The modified polymer displayed amphiphilic behavior, characterized by a critical aggregation concentration of 0.25% (w/v), and demonstrated efficient emulsifying properties. Ca-XG was incorporated into fusidic acid emulgels, where sixteen formulations were evaluated for their physicochemical and functional characteristics. All samples showed homogeneous appearance, with pH values ranging between 5.95± 0.297 to 6.83 ± 0.352, consistent with dermal compatibility. The formulations exhibited good spreadability (32.17–66.91 cm²) and stable drug content (1.96–1.99%). Among them, the optimized formulation provided sustained permeation of fusidic acid over 24 h, with a cumulative permeation of 16.67 mg/cm² and a steady-state flux of 0.724 mg/cm².h. Furthermore, diffusion coefficients (0.015–0.051 cm²/h) confirmed the ability of Ca-XG to control drug transport while ensuring hydration of the topical matrix. Overall, these results demonstrate that Ca-XG acts not only as a bio-based emulsifier but also as a multifunctional excipient, supporting controlled drug. Graphical