Box-Behnken Design Assisted Optimization and Characterization of Chitosan Film for Simultaneous Topical Delivery of Ascorbic Acid and Metronidazole

<b>Background/Objectives:</b> The objective of this study was to develop chitosan films plasticized with glycerol for the topical delivery of ascorbic acid and metronidazole. <b>Methods:</b> The films were prepared using a casting technique in which an aqueous ascorbic acid solution served as the solvent, eliminating the need for additional mineral or organic acids. The influence of compositions on film characteristics-specifically mechanical properties and surface pH-was examined, and an optimized formulation was identified using a Box-Behnken design-response surface methodology. Relevant characterization techniques and in vitro evaluations were conducted to assess the properties and performance of the optimized film formulation. <b>Results:</b> Results showed that both glycerol and ascorbic acid contributed to the plasticization of the films. Fourier-transform infrared spectroscopic analysis of the optimized film revealed the formation of chitosan ascorbate and interactions between chitosan and glycerol. In addition, the thermogram and powder X-ray diffractogram demonstrated alterations in the thermal behavior and crystallinity of the embedded bioactive compounds. The developed film possessed the preferred swelling capacity. Moreover, in vitro release studies revealed a co-release pattern, delivering both bioactive compounds simultaneously. <b>Conclusions:</b> These findings suggest that the prepared chitosan-based film could serve as a promising platform for topical delivery.