Physical properties and pH-dependent release kinetics of ascorbic acid from porous alginate films

In this study, a series of alginate-based films were prepared using a sodium alginate matrix in the presence of poly(vinyl alcohol) (PVA, M_w 67,000 g mol⁻¹) at three different concentrations (0.02%, 0.1%, and 0.5%). The film-forming solutions were cast and subsequently cross-linked with free Ca²⁺ ions in a calcium chloride solution to obtain porous structures. Scanning electron microscopy confirmed that pore formation was strongly influenced by the initial PVA content, enabling controlled porosity within the alginate network. The films were further characterized in terms of their physical properties, including thickness, opacity, moisture content, water solubility, swelling behavior at pH 5.5 and 7.4, and Ultraviolet-Visible (UV-VIS) light transmittance. Principal component analysis (PCA) was applied to evaluate the relationships among the measured physical properties. The films were loaded with ascorbic acid, and release studies revealed a pH-dependent release profile, with minimal release at acidic pH (5.5) and enhanced release at physiological pH (7.4). These findings indicate that the porous alginate-based films can function as smart, pH-responsive materials with potential application in controlled ascorbic acid delivery for wound dressing applications.