Sodium-activated Algerian bentonite with improved surface properties and topical barrier performance

This study investigates whether sodium activation can turn an under-utilized Algerian calcium bentonite into a topical barrier-oriented clay with measurable barrier-relevant performance in a model of inflammatory skin barrier dysfunction. Raw bentonite from the Hamma Boughrara deposit (Tlemcen, Algeria) was purified and activated to obtain a sodium-enriched clay (MEA5). We systematically related mineralogical, textural, interfacial properties and selected pharmacopeial quality tests to in vivo performance in an irritant contact dermatitis model. Sodium activation yielded a montmorillonite rich clay with increased specific surface area and cation exchange capacity, a lower pH_PZC and a stable negative ζ-potential at skin relevant pH, consistent with enhanced swelling, dispersion and colloidal stability. MEA5 met pharmacopeial limits for the quality tests performed. In vivo, topical MEA5 dispersions (2-10% w/v) were well tolerated in an acute dermal toxicity study and significantly reduced croton oil induced ear edema, with maximal inhibition at intermediate concentrations and a magnitude in the same order as the indomethacin reference under the same experimental conditions. These findings link sodium induced changes in interfacial properties of a local bentonite to its barrier forming and edema-inhibition outcome in vivo, and support MEA5 as a promising topical excipient candidate for formulations targeting compromised and inflamed skin.