Toxicity evaluation following intratracheal instillation of iron oxide in a silica matrix in rats

Abstract

Iron oxide-silica nanoparticles (IOSi-NPs) were prepared from a mixture of ferrous chloride tetrahydrate and ferric chloride hexahydrate dropped into a silica xerogel composite. The structure and morphology of the synthesized maghemite nanoparticles into the silica xerogel were analysed by X-ray diffraction measurements, scanning electron microscopy equipped with an energy dispersive X-ray spectrometer, and transmission electron microscopy. The results of the EDAX analysis indicated that the embedded particles were iron oxide nanoparticles. The particle size of IOSi-NPs calculated from the XRD analysis was estimated at around 12.5 nm. The average size deduced from the particle size distribution is 13.7 ± 0.6 nm, which is in good agreement with XRD analysis. The biocompatibility of IOSi-NPs was assessed by cell viability and cytoskeleton analysis. Histopathology analysis was performed after 24 hours and 7 days, respectively, from the intratracheal instillation of a solution containing 0.5, 2.5, or 5 mg/kg IOSi-NPs. The pathological micrographs of lungs derived from rats collected after the intratracheal instillation with a solution containing 0.5 mg/kg and 2.5 mg/kg IOSi-NPs show that the lung has preserved the architecture of the control specimen with no significant differences. However, even at concentrations of 5 mg/kg, the effect of IOSi-NPS on the lungs was markedly reduced at 7 days posttreatment.

Figure 1

Experimental (blue), calculated (solid line gray), and difference plot (lover line) of γ-Fe₂O₃ and silica.

Figure 2

SEM micrographs (a) and elemental maps of maghemite-silica nanocomposite.

Figure 3

TEM micrograph (high magnification at 180000x) showing the spherical IOSi-NPs, selected area electron diffraction (SAED), and size distribution.

Figure 4

DLS showing mean average size of maghemite-silica nanoparticles.

Figure 5

M-H curves of IOSi-NPs at room temperature in full scale (a) and in extended scale (b).

Figure 6

Cell viability data assessed by a MTT assay for hFOB 1.19 osteoblast cells incubated for 24 h (a) and 48 h (b) with the IOSi-NPs at various concentrations (25, 50, 75, and 100 μg/mL).

Figure 7

Cell viability data assessed by a MTT assay for HepG2 cells incubated for 24 h (a) and 48 h (b) with the IOSi-NPs at various concentrations (25, 50, 75, and 100 μg/mL).

Figure 8

F-actin—images of F-actin stained by FITC-Phalloidin (green), DAPI—images of nuclei stained with DAPI (blue), and merge—the merged picture. The cells were cultured for 24 h and 48 h in the presence of 50 and 100 μg/mL of IOSi-NPs.

Figure 9

Light optical image of the lung at 24 h after intratracheal instillation of IOSi-NPs in rats at various concentrations. The reference sample is also presented (a). Lung after 24 hours: control (a), 0.5 mg/kg (b), 2.5 mg/kg (c), and 5 mg/kg (d).

Figure 10

Light optical image of the lung at 7 days after intratracheal instillation of IOSi-NPs in rats at various concentrations. The reference sample is also presented (a). Lung after 7 days: control (a), 0.5 mg/kg (b), 2.5 mg/kg (c), and 5 mg/kg (d).

Figure 11

Light optical image of the liver at 24 h after intratracheal instillation of IOSi-NPs in rats at various concentrations. The reference sample is also presented (a). Liver after 24 hours: control (a), 0.5 mg/kg (b), 2.5 mg/kg (c), and 5 mg/kg (d).

Figure 12

Light optical image of the spleen at 24 h after intratracheal instillation of IOSi-NPs in rats at various concentrations. The reference sample is also presented (a). Spleen after 24 hours: control (a), 0.5 mg/kg (b), 2.5 mg/kg (c), and 5 mg/kg (d).