Antibacterial activity of trimetal (CuZnFe) oxide nanoparticles

Abstract

Background: The increasing resistance of pathogenic bacteria to antibiotics is a challenging worldwide health problem that has led to the search for new and more efficient antibacterial agents. Nanotechnology has proven to be an effective tool for the fight against bacteria.

Methods: In this paper, we present the synthesis and traits of trimetal (CuZnFe) oxide nanoparticles (NPs) using X-ray diffraction, high-resolution transmission electron microscopy, and energy dispersive x-ray spectroscopy. We evaluated the antibacterial activity of these NPs against gram-negative Escherichia coli and gram-positive Enterococcus faecalis and then compared it to that of their pure single-metal oxide components CuO and ZnO.

Results: Our study showed that the antibacterial activity of the trimetal oxide NPs was greater against E. coli than against E. faecalis. Overall, the antimicrobial effect of trimetal NPs is between those of pure ZnO and CuO nanoparticles, which may mean that their cytotoxicity is also between that of pure ZnO and CuO NPs, making them potential antibiotics. However, the cytotoxicity of trimetal NPs to mammalian cells needs to be verified.

Conclusion: The combination of three metal oxide NPs (ZnO, CuO, and Fe₂O₃) in one multimetal (CuZnFe) oxide NPs will enhance the therapeutic strategy against a wide range of microbial infections. Bacteria are unlikely to develop resistance against this new NP because bacteria must go through a series of mutations to become resistant to the trimetal oxide NP. Therefore, this NP can combat existing and emerging bacterial infections.

Keywords: Enterococcus faecalis; Escherichia coli; antibacterial agents; nanoparticles; nanotechnology; trimetal nanoparticles.

Figure 1

X-ray diffraction spectra of ZnO, CuO, and CuZnFe oxide nanoparticles. *Indicates that the peak is unidentified.

Figure 2

Scanning electron micrograph of the CuZnFe oxide nanoparticles.

Figure 3

(A) High-resolution transmission electron microscope micrograph of the mixed CuZnFe oxide nanoparticles (NPs). (B) Atomic resolution of mixed CuZnFe oxide NPs.

Figure 4

Energy dispersive x-ray spectroscopy spectrum of mixed CuZnFe oxide nanoparticles.

Figure 5

Percentage of live (A) Enterococcus faecalis (E. faecalis) cells and (B) Escherichia coli (E. coli) cells after 5 h of exposure to 150 µg/mL of metal oxide nanoparticles. Cells were grown in nutrient broth.

Figure 6

Ability of (A) Enterococcus faecalis (E. faecalis) and (B) Escherichia coli (E. coli) in nutrient broth to form biofilm after incubation with 150 µg/mL of metal nanoparticles as demonstrated by absorbance at 490 nm wavelength in a spectrophotometric reading.

Figure 7

Representative images of overnight growth of microbes on nutrient agar with no nanoparticles (NPs) or with 150 µg/mL of ZnO, CuO, or CuZnFe oxide NPs and their effect on the colony-forming unit/mL count: (A) Enterococcus faecalis, (B) Escherichia coli.

Figure 8

Colony-forming units (CFU) for (A) Enterococcus faecalis (E. faecalis) and (B) Escherichia coli (E. coli) after incubation in nutrient broth overnight with no nanoparticles (NPs) or in the presence of 150 µg/mL of metal oxides NPs.