Surface engineering of tin dioxide through chitosan: Band-gap tuning of spherical structure with oxygen vacancies for enhanced antibacterial therapeutic effects

Gram-negative (G-) bacteria-based infections have become a significant threat to global public health. These infections pose big challenges regarding treatment. The situation of emergency hospitalization due to bacterial infections requires alternative therapeutic strategies. To address these issues, the exploration of metal oxide hybrid NPs has significant attention for the development of new biocidal agents against bacterial infections. The antibacterial efficacy of SnO2 NPs depends on physio-chemical characteristics, including small particle size (decrease bacterial growth), the increasing band gap (increase redox capabilities), oxygen vacancies (ROS), leading to bacterial cell death. In the present work, the synthesized tin dioxide (SO) and chitosan-modified tin dioxide (CsSO) NPs exhibit the tetragonal rutile structure with spherical structure used to identify them by XRD and TEM analysis. The antibacterial activity of CsSO NPs was enhanced compared to SO NPs against (G-) bacterial strains. These small size (25 nm), bandgap (3.54 eV), and oxygen vacancies (505 & 537 nm) of CsSO NPs contribute to more ROS generation, leading to intracellular leakage and cell death. In vitro, the cytotoxicity of CsSO NPs showed lower toxicity to healthy fibroblast cells than that of SO NPs. These results confirmed that CsSO NPs are promising as bacterial agents for antibacterial therapy.