Proteasome inhibitory, antioxidant, and synergistic antibacterial and anticandidal activity of green biosynthesized magnetic Fe₃O₄ nanoparticles using the aqueous extract of corn (Zea mays L.) ear leaves

Figures & data

Figure 1. (A) UV-Vis spectrum of the Fe₃O₄ nanoparticles (inset: The ear leaves covering corn used for the synthesis of Fe₃O₄ nanoparticles and, FeCl₂ and FeCl₃ as the precursor compounds in aqueous extract of corn ear leaves (yellow) and synthesized Fe₃O₄ nanoparticles (black)); (B) Scanning electron microscopy (FE-SEM, inset: Selected Fe₃O₄ nanoparticle for EDX analysis); and (C) energy-dispersive X-ray spectroscopy (EDX, inset: elemental composition of Fe₃O₄ nanoparticle) of the Fe₃O₄ nanoparticles.

Figure 2. (A) Fourier-transform infrared spectroscopy [FT-IR; Fe₃O₄ nanoparticles (FeNPs) and aqueous extract of corn ear leaves (ELE)]; (B) Differential thermogravimetric (TG/DTG) spectra of Fe₃O₄ nanoparticles; (C) Vibrating sample magnetometer (VSM) graph of Fe₃O₄ nanoparticles (inset: indicates the magnetic properties of the synthesized Fe₃O₄ nanoparticles); and (D) X-ray diffraction (XRD) analysis of Fe₃O₄ nanoparticles.

Figure 3. Proteasome inhibitory (A) and antioxidant potential (B–E) of Fe₃O₄ nanoparticles. FeNP-10 and −100: Fe₃O₄ nanoparticle at a concentration of 10 and 100 μg/mL, respectively; Epox-1 and −10: epoxomicin at a concentration of 0.56 and 5.56 μg/mL, respectively; (B) ABTS radical scavenging assay; (C) Nitric oxide scavenging assay; (D) DPPH free radical scavenging assay; and (E) Reducing power assay. Different superscript letters indicate significant differences at P < 0.05.

Figure 4. Synergistic antibacterial and anticandidal potential of Fe₃O₄ nanoparticles. (A) Fe₃O₄ nanoparticles (25 μg) + kanamycin (5 μg); (B) Fe₃O₄ nanoparticles (25 μg) + rifampicin (5 μg); and (C) Fe₃O₄ nanoparticles (50 μg) + amphotericin b (5 μg).

Table 1. Synergistic antibacterial and anticandidal activity of Fe₃O₄ nanoparticles against foodborne pathogenic bacteria.

Synergistic antibacterial activity
Foodborne pathogens	Fe3O4 nanoparticles (25 μg/disc)	Kanamycin (5 μg/disc)	Rifampicin (5 μg/disc)	Fe3O4 nanoparticles + kanamycin	Fe3O4 nanoparticles + rifampicin
B. cereus ATCC 13061	0	0	0	9.87 ± 0.34^d*	0 ± 0.0^e
E. coli ATCC 43890	0	0	0	18.86 ± 0.82^b	0 ± 0.0^e
L. monocytogenes ATCC 19115	0	0	0	13.54 ± 0.30^c	0 ± 0.0^e
S. aureus ATCC 49444	0	0	0	13.09 ± 0.15^c	20.90 ± 0.50^a
S. typhimurium ATCC 43174	0	0	0	13.3 ± 0.47^c	0 ± 0.0^e
Synergistic anticandidal activity
Candida species	Fe3O4 nanoparticles (50 μg/disc)	Amphotericin b(5 μg/disc)		Fe3O4 nanoparticles + amphotericin b
C. albicans KACC 30003	0 ± 0	0 ± 0		9.37 ± 0.31^d*
C. albicans KACC 30062	0 ± 0	0 ± 0		16.69 ± 0.10^a
C. glabrata KBNO 6P00368	0 ± 0	0 ± 0		10.39 ± 0.37^c
C. glochares KACC 30061	0 ± 0	0 ± 0		15.97 ± 0.58^b
C. saitoana KACC 41238	0 ± 0	0 ± 0		10.59 ± 0.18^c

*Data are expressed as the mean zone of inhibition in mm ± standard deviation (SD). Values with different superscript letters are significantly different at P < 0.05.