Nano-silver-modified polyphosphazene nanoparticles with different morphologies: Design, synthesis, and evaluation of antibacterial activity

Drug-resistant bacteria present a severe threat to public health, emphasizing the importance of developing broad-spectrum antibacterial agents that are free from drug resistance. Among silver-based antibacterial agents, nano-silver has been found to exhibit the most promising and comprehensive performance. The exploration of the antibacterial capacity and morphological changes of silver nanoparticles (AgNPs) could offer a starting point for the development of safe and efficient antibacterial agents. In this study, three types of nano-silver-modified polyphosphazene (PRV) nanoparticles with different morphologies were synthesized using precipitation polymerization. These nanoparticles were characterized using various techniques, including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The antibacterial activity of these nanoparticles against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was assessed using minimum inhibitory concentration (MIC)/minimum bactericidal concentration (MBC) tests and inverted fluorescence microscopy. Our results revealed that the antibacterial activity of silver nanoparticles can vary significantly depending on their immobilized form. Ag@PRV Strawberry-like nanoparticles (NPs) exhibited higher antibacterial activity compared to Ag@PRV Yolk-Shell NPs and Ag@PRV Cable-like nanofibers (NFs). Notably, all three types of synthesized nanoparticles demonstrated a stronger bactericidal effect on Gram-positive bacteria than Gram-negative bacteria. Live/dead bacterial staining and scanning electron microscopy demonstrated that silver can kill bacteria by altering the permeability of their cell membranes. These findings offer valuable insights for designing and practically applying new silver-based antibacterial agents in the future.