Bacitracin-conjugated superparamagnetic iron oxide nanoparticles: Synthesis, characterization and antibacterial activity

Bacitracin-conjugated superparamagnetic iron oxide (Fe₃O ₄) nanoparticles were prepared by click chemistry and their antibacterial activity was investigated. After functionalization with hydrophilic and biocompatible poly(acrylic acid), water-soluble Fe ₃O₄ nanoparticles were obtained. Propargylated Fe ₃O₄ nanoparticles were then synthesized by carbodiimide reaction of propargylamine with the carboxyl groups on the surface of the iron oxide nanoparticles. By further reaction with N₃-bacitracin in a Cu^I-catalyzed azide-alkyne cycloaddition, the magnetic Fe ₃O₄ nanoparticles were modified with the peptide bacitracin. The functionalized magnetic nanoparticles were characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, TEM, zeta-potential analysis, FTIR spectroscopy and vibrating-sample magnetometry. Cell cytotoxicity tests indicate that bacitracin-conjugated Fe₃O₄ nanoparticles show very low cytotoxicity to human fibroblast cells, even at relatively high concentrations. In view of the antibacterial activity of bacitracin, the biofunctionalized Fe₃O₄ nanoparticles exhibit an antibacterial effect against both Gram-positive and Gram-negative organisms, which is even higher than that of bacitracin itself. The enhanced antibacterial activity of the magnetic nanocomposites allows the dosage and the side effects of the antibiotic to be reduced. Due to the antibacterial effect and magnetism, the bacitracin-functionalized magnetic nanoparticles have potential application in magnetic-targeting biomedical applications.