Possible Cytotoxic Effects of Silver Nanoparticles on the Parotid Glands of Albino Rats

Background: Silver has found to have many uses in the medical field due to its unique properties on the nanoscale, therefor the toxicity of nanosilver has become a hot topic and interesting area of research.
Aim of the study: The study aimed to explore whether the silver nanoparticles (AgNPS) have a cytotoxic effect on the parotid gland of male albino rats.
Materials and methods: The sample of study consisted of 30 adult male albino rats whose average body weight ranged from 250 to 300 grams and they were divided into two groups: Group 1 was consisted of 10 rats and served as controls, they received 0.5 ml deionized water per os using curved metallic oro-pharyngeal tube for 21 days. Group 2 was consisted of 20 rats, they received 10mg/kg b.w/day AgNP solution (in deionized water) with particle sizes ranging from 3 to 20 nm per os using curved metallic oro-pharyngeal tube (the recommended dose of each rat is 1.5-1.8 mg dissolved in 0.5 ml deionized water) for 21 days. The animals were observed for any body weight changes. The 30 rats were sacrificed after ending the experiment and dissection and separation were applied to their parotid salivary glands which were then fixed in 10% neutral buffered formalin. Afterwards, they were processed, fixed in paraffin, separated and stained with: 1-Hematoxylin and Eosin for histological evaluation of the parenchymal and stromal elements of the glands to detect any histological changes. 2-Streptavidin-biotin immunohistochemical method for localization of Ki67 for detection of the proliferation of cells.
Results: The study found that the serous acini swelled with abnormal architecture and ill-defined outline. In addition, the study could not distinguish the lining cells of the serous acini. The serous acinar cells showed deeply stained, large hyperchromatic nuclei and mitotic cell division of the acinar cells. Focal oncocytic changes of acinar cells were observed. There was a dilation of the excretory ducts with wide lumen and they were vacuolated degenerated thick epithelial lining. As a result of the effect of the AgNPs, the connective tissue septa of the parotid glands widened and resulted in an in increase in the fibrosis with chronic inflammatory cells infiltration. Blood vessels showed dilatation and engorged with RBCs. In the lobes of parotid gland, the focal areas revealed that their secretory elements have been completely degraded, resulting in a large empty vacuole which was surrounded by deep infiltration of chronic inflammatory cells. Immunohistochemical examination revealed intense nuclear and cytoplasmic Ki67 immunoreactivity of acinar cells, ductal cells and endothelial cells lining blood vessels.
Conclusion: Silver nanoparticles causing dramatic changes in the parotid gland. Even though, AgNPs have several therapeutic uses, their toxicity and therapeutic benefits should be weighed before a clinical decision to use them is reached.