الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 150 |  |  |
| | | from | 150 | | |
Abstract
Nanotechnology has currently become a combined science that is most typically utilized in different fields of science. Now a day’s, new forms of silver having particle size less than 100nm, i.e. silver nanoparticles (AgNPs) comes into focus due to its anti-bacterial activity, anti-viral and anti-tumor activity as well as antiplatelet property. Besides undeniable contribution towards oral health of AgNPs against infecting microbes and producing diseases, serious adverse events must be addressed to fulfil its safety requirements.
The aim of this investigation was to study the potential impacts of oral administration of silver nanoparticles on the submandibular salivary glands of albino rats and the possible effect of one-month recovery period.
Materials and Methods:
Forty-six adult male albino rats with an average of 150-180 grams body weight, were divided randomly into two groups as follows:
• group 1 consisted of 16 rats (4 rats per cage), served as controls. They were subdivided into two subgroups:
Subgroup 1.1 consisted of 8 rats, they received 0.5 ml deionized water per os using curved metallic oro-pharyngeal tube for 21 days.
Subgroup 1.2 consisted of 8 rats, they were treated the same way as subgroup 1.1 and then left untreated for one more month.
• group 2 consisted of 30 rats (5 rats per cage), 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 for each rat (1.5-1.8mg) was dissolved in 0.5 ml deionized water. They were divided into two subgroups.
110
Summary
Subgroup 2.1 consisted of 15 rats and treated for 21 days.
Subgroup 2.2 consisted of 15 rats, treated for 21 days and then left untreated for one more month as a recovery period.
The sections from submandibular salivary gland of rats were processed and stained by hematoxylin and eosin stain for histological examination and immunohistochemical stain for localization of cytokeratin in the glandular tissue. Other small specimens one cubic mm were cut and processed for ultrastructural examination by TEM.
Results:
Histological examination of the submandibular salivary glands of the silver nanoparticle group revealed marked degeneration in the parenchymal elements of submandibular salivary gland. There was apparent shrinkage and reduction in size and number of all the parenchymal elements including the acini and ducts in comparison to the controls. The serous acinar cells appeared with a lot of cytoplasmic vacuolization. The intercalated ducts showed marked shrinkage with cytoplasmic vacuolization. The GCTs showed loss of regular configuration, the striated duct showed cytoplasmic vacuolization and loss of basal striations. The excretory ducts showed loss of their pseudo-stratification and thickening in their lining cells. The connective tissue septa showed marked degeneration of its collagen fibers with chronic inflammatory cell infiltrate. Neighboring blood vessels appeared dilated and congested with RBCs.
Specimens of the recovery group showed marked improvement of their histological picture in comparison to those of the silver nanoparticles group. Acinar cells and granular convoluted tubules (GCTs) showed almost normal texture with no or little cytoplasmic vacuolization. Striated ducts regained their basal striations. However, apparent thickening was observed in their epithelial lining. The excretory ducts possessed cell lining with the pseudostratified
111
Summary
columnar epithelial appearance with their nuclei showing obvious mitotic figures, thickening in their epithelial lining. An increase in fibrous CT content surrounding ducts was sometimes recorded.
Ultrastructural results:
The electron microscopic examination of the submandibular glands of the silver nanoparticles group revealed that the secretory cells showed marked atrophic changes. There was accumulation of electron-lucent secretory granules, a lot of shrunken nuclei, marked dilation of rough endoplasmic reticulum (RER), a lot of cytoplasmic vacuolations, marked cell organelle degeneration, and destroyed and ruptured mitochondria which lost their cisternae. The intercalated, striated, granular convoluted tubules and excretory ducts showed multiple intracytoplasmic vacuoles representing damaged areas of cytoplasm with severe loss of cell organelles and stagnation of secretion in their lumens.
Specimens of the recovery group revealed marked improvement in comparison to those of the silver nanoparticles group with mild ultrastructural alterations.
Immunohistochemical results
Immunohistochemical localization of the cytokeratin in the parenchyma of the submandibular glands showed strongly positive staining reaction in the ducts and positive staining reaction in the serous acinar cells of the control group, while the silver nanoparticles group showed a weakly positive staining reaction in most of the gland’s elements. Marked improvement was observed in the recovery group where they showed almost strongly and moderately positive staining reaction similar to the control group.