Synthesis and characterization of nanoscale zeolitic imidazolate frameworks with ciprofloxacin and their applications as antimicrobial agents

The present study investigated antibiotic drug loading in metal-organic frameworks (MOFs). Porous zeolitic imidazolate frameworks (ZIFs) were synthesized under concentrated aqueous solution. A straightforward nano-precipitation method was used to prepare ciprofloxacin (CIP)-loaded ZIF-8 (CIP-ZIF-8). ZIF-8 and CIP-ZIF-8 were characterized by FT-IR spectroscopy, X-ray powder diffraction, scanning electron microscopy, thermogravimetric analysis, the BET nitrogen adsorption-desorption method, and UV-Vis spectroscopy. The thermal behavior of CIP-ZIF-8 was confirmed by thermal analyses. FT-IR spectroscopy illustrated the presence of functional groups of CIP and ZIF-8 frameworks in CIP-ZIF-8. ZIF-8 showed high loading capacity for the model antibiotic drug CIP with pH-sensitive release. The as-synthesized CIP-ZIF-8 possesses high drug loading efficiency (21%), and the release in pH 5.0 acetate buffer solutions (97%) was faster than in pH 7.4 phosphate buffers (83%). The antibacterial activities of ZIF-8 and CIP-ZIF-8 were tested against one Gram-positive and one Gram-negative species. The results showed that the synthesized materials had good growth inhibition against microorganisms.