Chitosan quaternary ammonium salt-stabilized cerium oxide nanoparticles green-synthesized using <i>Thymus vulgaris</i> extract: multifunctional antibacterial, anticancer, and wound healing applications

This study presents the synthesis and biological evaluation of chitosan quaternary ammonium salt-stabilized cerium oxide nanoparticles (CS/CeO₂NPs), green-synthesized using <i>Thymus vulgaris</i> (thyme) extract. Characterization through Fourier Transform Infrared Spectroscopy (FTIR), Field-Emission Scanning Electron Microscopy (FESEM), and X-ray Diffraction (XRD) revealed uniform spherical nanoparticles with an average size of 120 nm and crystalline structure with an average crystal size of 28.32 nm. The incorporation of thyme extract into the CS matrix was confirmed. Drug release studies exhibited a biphasic pattern, with a rapid initial release (75.41% in 3 h) followed by a sustained release, achieving 92.56% over 10 days. Antibacterial assays demonstrated dose-dependent efficacy against <i>Staphylococcus aureus</i>, with significant antibacterial activity at concentrations above 60 μg/mL. <i>In vitro</i> anticancer assays revealed potent cytotoxicity against breast cancer (MCF-7) and colon cancer (CT26) cell lines, with 50% inhibition in MCF-7 and over 80% inhibition in CT26 cells at 60 μg/mL. <i>In vivo</i> evaluations further highlighted the therapeutic potential of CS/CeO₂NPs. Wound-healing assays demonstrated accelerated wound closure and enhanced epithelial regeneration in CS/CeO₂NPs-treated rats. <i>In vivo</i> antibacterial assays showed significant bacterial load reduction, particularly against <i>S. aureus</i>, indicating effective infection control. Histological analysis confirmed improved tissue regeneration, reduced inflammation, and enhanced re-epithelialization in CSQ/CeO₂NPs-treated wounds, suggesting efficient wound healing. These results underscore the multi-functional therapeutic potential of CS/CeO₂NPs, highlighting their antibacterial, antioxidant, anticancer, and wound-healing properties. Further research is needed to optimize formulations and elucidate the mechanisms driving their biological activities for clinical applications.