Preliminary evaluation of surface functional properties of chitosan films reinforced with TiO₂ or ZnO nanoparticles

• Different nanoparticle types were combined to tailor chitosan surface functionality. • The low contents of fillers prevented interfacial defects and phase separation. • The effects of TiO₂ or ZnO led to improved functional performance at low filler contents. • Biodegradable films with improved surface properties were obtained, making them potential candidate materials for packaging applications. Biodegradable polymers have garnered increasing attention as eco-friendly alternatives to conventional petroleum-derived plastics, which pose a global environmental challenge due to their difficult recycling and slow degradation. This study focuses on the preliminary evaluation of surface functional properties of chitosan films reinforced with TiO₂ or ZnO nanoparticles (NPs). These films were prepared at different loading ratios using the solution-casting method. Structural and morphological properties were characterized using FTIR and FESEM, while functional properties were evaluated by surface wettability, UV-Vis spectroscopy, thermogravimetric analysis and antibacterial activity testing. FTIR results showed significant changes in absorption peaks associated with amine and hydroxyl groups, indicating the formation of hydrogen bonds and strong surface interactions between chitosan and NPs. Morphological imaging also revealed a nanoscale surface structure that could influence wettability and surface interactions. The results of functional tests, compared to pure chitosan, showed improvements in some functional properties, like UV protection and thermal stability, while maintaining other properties, like surface wettability, within accepted functional limits. Moreover, chitosan films reinforced with TiO₂ or ZnO NPs showed statistically significant antibacterial activity, particularly against S. aureus. These results represent a preliminary evaluation of potential candidate materials for packaging applications. Therefore, a comprehensive evaluation of the studied samples and their suitability for practical applications requires further future studies that include tests of mechanical properties, gas permeability, biodegradability, migration and biosafety studies and performance under real-world application conditions.