Iron oxide/silver-doped iron oxide nanoparticles: facile synthesis, characterization, antibacterial activity, genotoxicity and anticancer evaluation

Abstract

Iron oxide nanoparticles (IONPs) are extremely sought after due to their antibacterial, antioxidant, and anticancer properties. IONPs were synthesized from Pseudomonas aeruginosa kb1 extracellular supernatant extract. After 48 h at 37 °C in the precursor iron salt, the weak yellow culture supernatant turned yellowish-brown and brown-black, confirming IONP production. To make Ag-doped IONPs, sodium borohydride (NaBH₄) reduced the silver nitrate (AgNO₃) salt on the biosynthesized IONPs. SEM showed that the nanoparticles clustered and had a uniform size distribution and approximately spherical shape. EDX and XRD analysis validated the production of maghemite (γ-Fe₂O₃) and magnetite (Fe₃O₄) IONPs. Fourier transform infrared spectroscopy determined the surface functional groups of Ag-doped and IONPs. The antibacterial activity of Fe₃O₄ and Ag-doped Fe₃O₄ NPs against numerous harmful bacterial strains was much higher than that of Fe₂O₃. The normal retina cell line and human lung cancer cell line A549 were also tested for cytotoxicity using the MTT assay. Ag-doped Fe₃O₄ NPs were more cytotoxic than IONPs on A549 cells. Therefore, the biosynthesized Ag-doped Fe₃O₄ NPs, rather than IONPs, have potential applications as pharmaceutical and therapeutic products because they are safe, eco-friendly, and cost-effective.

Keywords: Antibacterial; Anticancer activity; Cell Cytotoxicity; Genotoxicity; IONPs; Silver NPs doping.

Fig. 1

Biosynthesis of IONPs (a) before synthesis and (b) after synthesis of Fe₃O₄ NPs but (e) before synthesis and (f) after synthesis of Fe₂O₃ NPs using Pseudomonas aeruginosa kb1 bacterial supernatant. Nano-iron pellets were collected in Petri dishes after centrifugation, (c) before and (d) after drying in an oven at 80 °C for 20 h for the Fe₃O₄ NPs, whereas they were collected (g) before and (h) after drying for the Fe₂O₃ NPs.

Fig. 2

The scheme of synthesis process for IONPs and Ag-doped IONPs.

Fig. 3

UV–visible absorption spectra of (a) Fe₃O₄ NPs and Fe₂O₃ NPs synthesized from P. aeruginosa kb1, inset the photograph of the Fe₃O₄ NPs attracted by a magnet, and (b) Ag-doped Fe₃O₄ NPs and Ag-doped Fe₂O₃ NPs.

Fig. 4

FTIR spectra of the IONPs synthesized in green via magnetotactic bacteria and silver-doped IONPs: (a) bacterial extract, (b) Fe₂O₃ NPs, (c) Fe₃O₄ NPs, (d) bacterial extract with a wavenumber range of 400–1000 cm^−1, (e) Fe₂O₃ NPs with a wavenumber range of 400–1000 cm^−1, (f) Fe₃O₄ NPs with a wavenumber range of 400–1000 cm^−1, (g) Ag-doped Fe₃O₄ NPs, and (h) Ag-doped Fe₂O₃ NPs.

Fig. 5

FTIR spectra of the IONPs synthesized in green via magnetotactic bacteria: (a) Fe₂O₃ NPs, and (b) Fe₃O₄ NPs, and (c) digital photograph of Fe₃O₄ NPs powder attraction by a magnet.

Fig. 6

XRD patterns of the synthesized NPs (a) Fe₂O₃ NPs, (b) Fe₃O₄ NPs, (c) Ag-doped Fe₂O₃ NPs, and (d) Ag-doped Fe₃O₄ NPs.

Fig. 7

SEM micrographs of the synthesized NPs: (a) Fe₃O₄ NPs, (b) Fe₂O₃ NPs, (c) Ag-doped Fe₃O₄ NPs at different magnifications, (d) Ag-doped Fe₂O₃NPs.

Fig. 8

EDX analysis of the synthesized NPs (a) Fe₃O₄ NPs, (b) Fe₂O₃ NPs, (c) Ag-doped Fe₃O₄ NPs and (d) Ag-doped Fe₂O₃ NPs.

Fig. 9

Typical TEM images of the synthesized NPs at various magnifications: (a) Fe₃O₄ NPs, 1 μm, 0.5 μm, 200 nm, and 100 nm; (b) Fe₂O₃ NPs, 0.5 μm, 200 nm, and 100 nm; (c) Ag-doped Fe₃O₄ NPs, 200 nm, 100 nm, 50 nm; and equivalent SAED of Ag-doped Fe₃O₄ NPs; (d) Ag-doped Fe₂O₃ NPs, 200 nm, 100 nm, 50 nm; and equivalent SAED of Ag-doped Fe₂O₃ NPs.

Fig. 10

DLS and zeta potential of the synthesized IONPs. (a) DLS of Fe₃O₄ NPs, (b) zeta potential of Fe₃O₄ NPs, (c) DLS of Fe₂O₃ NPs, and (d) zeta potential of Fe₂O₃ NPs.

Fig. 11

DLS and zeta potential of the synthesized silver-doped IONPs. (a) DLS of Ag-doped Fe₃O₄ NPs, (b) zeta potential of Ag-doped Fe₃O₄ NPs, (c) DLS of Ag-doped Fe₂O₃ NPs, and (d) zeta potential of Ag-doped Fe₂O₃ NPs.

Fig. 12

Representative plates showing the antibacterial activity of IONPs. (a) Effects of various concentrations of Fe₃O₄ NPs and (b) Fe₂O₃ NPs against the tested pathogenic bacteria.

Fig. 13

The proposed mechanism of the antibacterial activity of IONPs against the bacterial cells.

Fig. 14

Representative plates showing the antibacterial activity of silver-doped iron NPs. (a, b) Ag-doped Fe₃O₄ NPs and (c, d) Ag-doped Fe₂O₃ NPs at various concentrations against the tested pathogenic bacteria.

Fig. 15

Growth curves of bacteria showing the effects of differently synthesized IONPs (Fe₃O₄ and Fe₂O₃) at different concentrations (5, 10, and 20 mg/ml) (a) E. coli, Fe₃O₄ NPs; (b) E. coli, Fe₂O₃ NPs (c) K. pneumoniae, Fe₃O₄ NPs (d) K. pneumoniae, Fe₂O₃ NPs.

Fig. 16

Growth curves of bacteria showing the effects of various concentrations of Ag-doped IONPs (0.5, 1, and 2 mg/ml). (a) E. coli, Ag-doped Fe₃O₄ NPs; (b) E. coli, Ag-doped Fe₂O₃ NPs; (c) K. pneumoniae, Ag-doped Fe₃O₄ NPs; (d) K. pneumoniae, Ag-doped Fe₂O₃ NPs.

Fig. 17

SEM micrographs of E. coli (a, c, and e) and K. pneumoniae (b, d, and f) before and after treatment with IONPs.

Fig. 18

Representative images of comet assays of E. coli and K. pneumoniae before and after treatment with (a) Fe₃O₄ and Fe₂O₃ NPs and (b) Ag-doped Fe₃O₄ and Ag-doped Fe₂O₃ NPs. Bar diagram of the mean values of the tail length of E. coli and K. pneumoniae before and after treatment with (c) Fe₃O₄ and Fe₂O₃ NPs and (d) Ag-doped Fe₃O₄ and Ag-doped Fe₂O₃ NPs.

Fig. 19

Bar diagram of in vitro anticancer studies of IONPs against a negative control lung carcinoma cell line. (a) Fe₃O₄ NPs, and (b) Fe₂O₃ NPs.

Fig. 20

Bar diagram of in vitro anticancer studies of Ag-doped IONPs against a negative control lung carcinoma cell line. (a) Ag-doped Fe₃O₄ NPs, and (b) Ag-doped Fe₂O₃ NPs.

Fig. 21

Bar diagram of in vitro anticancer studies of IONPs against a negative control colon cancer cell line. a: Fe₃O₄ NPs, b: Fe₂O₃ NPs.

Fig. 22

Bar diagram of in vitro anticancer studies of IONPs against the negative control normal retina cell line. a: Fe₃O₄ NPs, b: Fe₂O₃ NPs.

Fig. 23

Bar diagram of in vitro anticancer studies of Ag-doped IONPs against the negative control normal retina cell line. a: Ag-doped Fe₃O₄ NPs, b: Ag-doped Fe₂O₃ NPs.