Antibacterial performance of chitosan-modified magnesium fluoride nanoparticles: Synthesis and characterization

The rise of multidrug-resistant bacterial infections threatens human health by reducing the effectiveness of conventional antibiotics. This growing challenge highlights the urgent need for advanced nano-based antibacterial materials capable of overcoming resistance and providing broad-spectrum protection. In this study, magnesium fluoride (MgF₂) NPs and Chitosan modified MgF₂ (MgF₂-Cs) were synthesized via a facile wet-chemical route and characterized to evaluate their structural, surface, and antibacterial properties. XRD confirmed the formation of tetragonal MgF₂ with crystallite sizes of 29 nm for MgF₂ and 22 nm for MgF₂-Cs, the reduction attributed to Cs-induced surface modification. FTIR, PL, and XPS analyses verified successful Cs incorporation through the presence of -OH, -NH₂, CN, and O-C=O functional groups and the preservation of the MgF₂ lattice. DLS further supported increased hydrodynamic size upon polymer coating. PL analysis showed enhanced blue-green emission around 497 nm in MgF₂-Cs, suggesting increased defect density and corresponding ROS-generation ability. Antibacterial activity against Gram-positive:S. aureus, S. pneumoniae and Gram-negative:K. pneumoniae, S. dysenteriae bacteria demonstrated significantly improved inhibition for MgF₂-Cs, with zone diameters of 15-21 mm, surpassing MgF₂ (12-16 mm) and Cs (11-15 mm. The MIC and MBC values for MgF₂-Cs against K. pneumoniae were determined to be 0.6 mg mL^-1 and 0.9 mg mL^-1, respectively. The enhanced antibacterial performance is attributed to synergistic effects of defect-mediated ROS production and Cs-bacteria electrostatic interactions.