Preparation and characterization of metronidazole loaded film consisting of chitosan and ascorbic acid for topical application

This study presents the formulation and optimization of chitosan-based topical films incorporating ascorbic acid and metronidazole, designed as a biocompatible wound dressing with dual therapeutic action. Glycerol was used as a plasticizer to improve film flexibility and mechanical integrity. The films were fabricated using a solvent casting technique, wherein ascorbic acid functioned dually as a solvent and a stabilizing excipient—eliminating the need for conventional acidic solubilizers. A Box–Behnken design was applied to systematically investigate the effects of chitosan, ascorbic acid, and glycerol concentrations on critical film parameters, including tensile strength, elongation at break, and surface pH. The optimized formulation was characterized through a series of analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and powder X-ray diffraction (PXRD), to evaluate its structural, thermal, and molecular properties. Additionally, in vitro studies assessed the film’s swelling behavior, drug content, and release profiles. Results demonstrated that both glycerol and ascorbic acid significantly enhanced the film’s mechanical performance via plasticization, while FTIR and thermal analyses confirmed molecular interactions and altered crystallinity within the matrix. The optimized film exhibited uniform morphology, pH compatibility for skin application, and a biphasic co-release of the incorporated bioactives—supporting its suitability for wound healing applications.