Study on Synthesis and Antibacterial Properties of AgNPs@ZIF-67 Composite Nanoparticles

Bacterial infection and resistance have threatened public health and it is necessary to develop a novel and efficient antibacterial agent. Metal-organic frameworks (MOFs) have been widely studied and applied in the antibacterial field. The porous carbon frameworks could provide intrinsic conditions to avoid the agglomeration and avail the stabilization of metal nanoparticles, which may be some synergies. Herein, a novel kind of AgNPs@ZIF-67 composite nanoparticles was prepared by a green, rapid. and cost-effective method, during which zeolitic imidazolate framework-67 (ZIF-67) acted as a template and small silver nanoparticles (AgNPs) could be facilely prepared in situ by the reduction of silver ions with fresh sodium borohydride (NaBH4). Specifically, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images confirmed the existence of as-prepared AgNPs with average diameters of (7.05 +/- 0.09) run and the introduction of AgNPs did not alter the size and rhombic dodecahedron-type morphology of ZIF-67. Energy-dispersive X-ray spectroscopy (EDS) elemental mapping revealed that AgNPs@ZIF-67 mainly contained uniformly dispersed C, N, O, Co and Ag elements. And the loading ratio of Ag weight content was 0.98% in it. The X-ray diffraction (XRD) pattern of the AgNPs@ZIF-67 sample showed a series of typical and sharp diffraction peaks in the (011), (002), (112), and (222) planes but no obvious peaks attributed to the AgNPs, which exhibited the formation of phase-pure ZIF-67 and well-dispersed of metallic Ag in ZIF-67. Zeta potentials showed a higher potential of ZIF-67 ( +25.6 mV) than AgNPs@ZIF-67 (+17.7 mV), indicating the load of negative charged AgNPs and good stability of the as-obtained AgNPs@ZIF-67. Furthermore, Staphylococcus aureus (S. aureus) (ATCC 6538) was used in the antibacterial assay and the bacterial concentration was regarded as 1 x10(8) CPU.mL(-1) when the OD600 value of the suspensions was 0.1. The in vitro minimum inhibitory concentration (MIC) of AgNPs@ZIF-67, ZIF-67 were 300, 350 mu g.mL(-1) , respectively. The antibacterial efficiency of AgNPs@ZIF-67, ZIF-67, and AgNPs at 24 h were 99.889%, 57.192%, and 26.433%, respectively. It was illustrated that the decoration of AgNPs could signifi cantly improve the antibacterial ability of ZIF-67 nanomaterials. Moreover, SEM images of S. aureus showed that AgNPs@ZIF-67 did more serious damage to the cell membrane than ZIF-67. This work provided a facile method to fabricate the AgNPs@ZIF-67 composite nanoparticles, which was demonstrated as a promising antibacterial material based on the synergistic effect of AgNPs and ZIP-67.