Alginate-based spray-dried microparticles for co-encapsulation of vitamins and minerals: Effects on structure, release behaviour, and transdermal delivery

Micronutrient delivery systems must combine compounds with different physicochemical properties while maintaining stability and controlled release. This study investigated the feasibility of using alginate-based spray-dried microparticles for the encapsulation and co-encapsulation of vitamins C, B12, and E, together with the minerals iodine and iron. These micronutrients were selected as representative hydrophilic and lipophilic compounds commonly associated with stability and bioavailability challenges. Microparticles were successfully produced using sodium alginate as a carrier, yielding spherical structures with porous morphology and mean particle sizes ranging from 7.31 ± 0.01 to 15.06 ± 0.09 μm. Structural characterization by FTIR confirmed the preservation of alginate functional groups, indicating that no new chemical bonds were formed during encapsulation. In vitro release studies performed in ethanol and phosphate-buffered saline (PBS) demonstrated that release kinetics were strongly dependent on both formulation composition and release medium. Diffusion-controlled transport was predominant in most systems, although co-encapsulation modified release behaviour, with certain micronutrients exerting a dominant influence on overall transport profiles. The results further highlight the role of alginate matrix swelling and solvent–polymer interactions, where aqueous environments promote polymer relaxation and diffusion, while ethanol limits matrix expansion. Ex vivo permeation assays indicated that encapsulation does not significantly hinder transport across the skin barrier but may influence the release stage prior to permeation. Overall, the results provide insight into the structure–property–function relationships governing alginate-based multi-component delivery systems and demonstrate the potential of spray-dried polysaccharide matrices for the controlled delivery of micronutrients in food, pharmaceutical, and topical formulations.