Impact of biosynthesized silver nanoparticles cytotoxicity on dental pulp of albino rats (histological and immunohistochemical study)

Abstract

This study aimed to evaluate the potential cytotoxic effect of oral administration of silver nanoparticles (Ag-NPs) on adult albino rats' pulp tissue; due to the enormous uses of Ag-NPs in the medical and dental field. The Ag-NPs were synthesized via the green process using peels of pomegranate extract. The pomegranate-mediated Ag-NPs were subjected to morphological and spectral analysis through ultraviolet visible absorption spectra, transmission electron microscopy, Fourier transforms infrared, Zeta-potential measurements, and energy dispersive X-ray spectroscopy. The structural and morphological characterization techniques confirmed the proper synthesis of biosynthesized Ag-NPs with a size around 20 ​nm and the surface plasmon resonance peak within 400-450 ​nm. The oral cytotoxic effect of Ag-NPs was assessed through detecting the histological (hematoxylin & eosin, Masson's trichrome) and immunohistochemical (vascular endothelial growth factor (VEGF), Caspase-3 proteins) variations. The data was analyzed statistically through using the SPSS software. Dental pulp tissues of albino rats-treated with Ag-NPs revealed that most of the odontoblasts with marked hydropic degeneration, vacuolization of their cytoplasm, loss of organization and apoptosis. Marked vasodilatation and cognition of blood vessels were detected. There was weak to moderate positive reactivity to Masson's trichrome stain. There was statistically significant decrease in the expression of VEGF in the treated group and highly statistically significant increase in the expression of Caspase-3 in comparison with the control group.

Conclusion: Oral administration of Ag-NPs induced size and dose-dependent structural changes in the pulp tissue of adult male albino rats.

Keywords: Caspase-3; Cytotoxicity; Dental pulp; Silver nanoparticles; VEGF.

Fig. 1

Photographs showing the structural and morphological characterization of biosynthesized Ag-NPs. (a) The TEM image of biosynthesized Ag-NPs. (b) Its SAED pattern. (c) EDX pattern of Ag-NPs. (d) zeta potential of Ag-NPs. (e) UV–Vis absorption spectra between the extract and Ag-NPs. Note: the color changing. (f) FTIR spectra for the rice husk extract and Ag-NPs.

Fig. 2

Histological photomicrographs showing the pulp tissue stained with H& E stain (A: F) and Masson trichrome stain (G: I). A, B) showing the pulp of the control group with normal histological structure; odontoblastic layer O, cell-free zone CF, cell-rich zone CR and central pulp core PC (X 100 & 400). C: E) showing the pulp of Ag-NPs-treated group with odontoblastic atrophy and degeneration O, separation of the odontoblastic layer from dentin black arrow, tissue degeneration in the pulp core star, congestion of blood vessels with RBCs blue arrow, extravasation of RBCs green arrow, and occlusion of blood vessels black arrow heads (X 400). F) showing marked hydropic/fatty degeneration in the odontoblastic and sub odontoblastic layer with massive infiltration of inflammatory cell (X 400). G) showing strongly positive reactivity of the collagen fibers with Masson’s trichrome stain in the negative control group (X 400). H, I) showing weak to moderate positive reactivity to the Masson’s trichrome stain in Ag-NPs-treated group (X 400).

Fig. 3

Photomicrographs of immunohistochemical-stained sections of the pulp tissue of different groups (X400). A) Control group showing moderately positive staining reactivity to VEGF mono-colonal antibody. B, C) Treatment group showing marked reduction in the staining reactivity to VEGF. D) Control group showing weak positive staining reaction to caspase 3 mono-colonal antibody. E, F) Treatment group showing strong positive staining reaction of pulp cells, fibers & blood vessels to caspase 3.