Evaluation of the Antimicrobial and Organic Dye Removal Properties of Silver-Incorporated ZIF-L Metal-Organic Framework Nanoparticles

Bacterial resistance to antimicrobial agents is a serious problem encountered all over the world. With the misuse of antimicrobial agents for the treatment of human and animal diseases, large quantities of these agents find their way into our environment, polluting water and soil. Further, with industrialization and urbanization, several organic dyes are used as colorants for products. The waste products from such manufacturing processes find their way into our environment, especially in the less developed world. There is an urgent need to remediate the effects of organic dyes and develop a new class of materials that can tackle the effects of antimicrobial resistance. In this regard, the research in this paper pertains to the development of zinc imidazolate metal-organic framework (ZIF-L) nanoparticles and evaluation of their antimicrobial effects on both standard and clinically isolated strains of Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Pseudomonas aeruginosa (P. aeruginosa). Further, in this work, we evaluated the removal of organic dyes using ZIF-L and Ag/ZIF-L nanoparticles. The synthesized nanoparticles were characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), thermal gravimetric analysis (TGA), UV-visible absorption spectroscopy, and band-gap energy analysis. The results for the antibacterial study showed that Ag/ZIF-L nanoparticles were superior to ZIF-L against S. aureus and P. aeruginosa strains tested, where the minimum bactericidal concentration (MBC) of Ag/ZIF-L was 2.5 mg/mL, whereas the MBC of ZIF-L was more than 10 mg/mL. In the case of E. coli strains, ZIF/L showed a better MBC value of less than 1.25 mg/mL, whereas for Ag/ZIF-L it was more than 1.25 mg/mL. Further, Ag/ZIF-L nanoparticles coated on a face mask and cotton gauze demonstrated superior antimicrobial activity compared to uncoated gauze and mask, whereas the Ag/ZIF-L-coated mask and gauze showed the zone of inhibition (ZOI) for all of the bacteria with P. aeruginosa having a higher ZOI value than S. aureus and E. coli. For quantification of the removal of organic dyes, ZIF-L and Ag/ZIF-L nanoparticles showed complete methylene blue dye removal from the solution at 150 min in the presence of sunlight. Under dark conditions, only 83% dye was removed by Ag/ZIF-L and 65% by ZIF-L. The results show that ZIF-L metal-organic frameworks have the potential to be used for clinical and environmental remediation applications.