ZnO@ZIF-8 Nanoparticles as Nanocarrier of Ciprofloxacin for Antimicrobial Activity

Abstract

Numerous antimicrobial drugs have been prescribed to kill or inhibit the growth of microbes such as bacteria, fungi, and viruses. Despite the known therapeutic efficacy of these drugs, inefficient delivery could result in an inadequate therapeutic index and several side effects. In order to overcome this adversity, the present study investigated antibiotic drug loading in zeolitic imidazolate frameworks (ZIFs), in association with ZnO nanoparticles with known antimicrobial properties. In an economic synthesis method, the ZnO surface was first converted to ZIF-8 with 2-methylimidazole as a ligand, resulting in a ZnO@ZIF-8 structure. This system enables the high drug-loading efficiency (46%) of an antimicrobial drug, ciprofloxacin, within the pores of the ZIF-8. This association provides a control of the release of the active moieties, in simulated body-fluid conditions, with a maximum of 67% released in 96 h. The antibacterial activities of ZnO@ZIF-8 and CIP-ZnO@ZIF-8 were tested against the Gram-positive Staphylococcus aureus strain and the Gram-negative Pseudomonas aeruginosa strain, showing good growth inhibition. This result was obtained by combining ZnO@ZIF-8 with ciprofloxacin in a minimal inhibitory concentration (MIC) that was 10 times lower than ZnO@ZIF-8 for S. aureus and 200 times lower for P. aeruginosa, suggesting that CIP-ZnO@ZIF-8 may have potential application in prolonged antimicrobial treatment.

Keywords: ZnO; antimicrobial activity; metal-organic framework; nanoparticles.

Figure 1

Schematic of ZnO@ZIF-8 NPs formation.

Figure 2

XRD patterns of ZnO NPs, ZIF-8 NPs, and ZnO@ZIF-8 NPs (A); FTIR spectra of ZIF-8 and ZnO@ZIF-8 NPs (B).

Figure 3

SEM images (A,B) and particle size distribution (C) of ZnO@ZIF-8 particles.

Figure 4

XRD analysis of CIP-ZnO@ZIF-8 after incorporation assays (A), with shift peak identification (A1) and identification of ZnO after incorporation (A2); TGA analyses of CIP, ZnO@ZIF-8, and CIP-ZnO@ZIF-8 (B); Zeta potential measurements for ZnO, ZIF-8, ZnO@ZIF-8, CIP, and CIP-ZnO@ZIF-8 NPs (n = 3) (C).

Figure 5

N₂ adsorption–desorption isotherms and BET surface areas (inset table) of ZnO@ZIF-8 and CIP-ZnO@ZIF-8.

Figure 6

Profile of CIP release from ZnO@ZIF-8 into PBS solution at pH 7.4, at 37 °C. The data were fit to the Korsmeyer–Peppas equation, as indicated by the red line.