الفهرس 
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Abstract
Gold nanoparticles are widely investigated for its efficient role in the field of biomedicine owing to its distinct physico-chemical and biological properties. It has been widely investigated for its broad spectrum properties which include antibacterial activity, drug delivery, gene transfer, detection of human pathogens, nucleic acid labelling, cosmetics, and as molecular theranostics.
Despite enormous potential, safety of AuNPs remains a controversial topic. from the large number of studies conducted to evaluate the toxicity of AuNPs, no definitive conclusions have been drawn due to the complexity of factors involved in their biological effects.
The aim of this investigation is to study the possible toxic effect of intraperitoneal administration of gold nanoparticles on the periodontal ligament of albino rats and the possibility of one month recovery period.
Summary and Conclusions
159
Forty-six adult male albino rats with an average 150-180-gram body weight were included in the study. They were divided into the following groups:
group 1: consisted of 16 rats, they received daily intraperitoneal injection of the solvent (deionized water 0.5 ml) for 21 days and served as controls.
Half the animals of the control group (sub-group 1.1) was euthanized after 21 days, while the other half (sub-group 1.2) was left for one more month, then euthanized.
group 2: consisted of 15 rats, they received daily intraperitoneal injection of 10mg/kg b.w of AuNP solution dissolved in 0.5 ml deionized water (particle sizes around 30 nm) for 21 days.
group 3: consisted of 15 rats, they were treated the same way as group 2 for 21 days and then left for 1 month as recovery period.
The experiment lasted for 21 days for group 2 then the rats were euthanized by cervical dislocation. While the rats of group 3 were euthanized by cervical dislocation after 1 month of treatment stoppage with nanogold for recovery, the lower jaws of each rat was dissected out, separated into two halves, the right halves were fixed in 10% neutral buffered formalin, decalcified in 10% EDTA solution.
After complete decalcification, the specimens of the molar region were processed and embedded in paraffin. Four microns thick sections were cut to be stained with:
- Hematoxylin and eosin stain for histological examination and detection of any structural changes in the periodontal ligament and surrounding alveolar bone. - Masson’s trichrome stain for detection of collagen fibers density.
Summary and Conclusions>160Specimens of the left side were immediately fixed in 2.5% glutaraldehyde, decalcified in 10% EDTA solution. After complete decalcification, very small samples (13mm) were taken from the investing tissues of the molar region in the mid root area, post fixed in osmium tetroxide, processed, embedded in epoxy resin. Ultrathin sections were cut and stained for transmission electron microscope examination.
a. Light and Electron Microscopic Results:-
1- group 1.1 and 1.2 (control group):-
Normal structure and ultrastructure of the collagen bundles that were either cut longitudinally or transversely extending between the bone and cementum were seen. According to the direction of section, the fibroblasts were either spindle, stellate or rounded in shape. The fibroblasts were presented with large rounded or oval nuclei with peripheral chromatin condensation. The nuclear membrane was smooth and regular. The cytoplasm showed abundant R.E.R., variable sized mitochondria, Golgi bodies and occasional lysosomal bodies. Neutrophils, mast cells, plasma cells and lymphocytes were sometimes encountered within the fibrous tissue of the PDL.
The alveolar bone showed normal appearance and turnover rate, as the number of the reversal lines were minimal. Besides, the PDL/ bone interface appeared to be smooth; no osteoclastic activity was observed.
2- group ӀӀ animals (treated with AuNPs):-
The PDL showed degenerative changes manifested as focal degeneration and loss of orientation of collagen fibers and apparent decrease in the number of fibroblasts. Frequent areas of loss of attachment of PDL fibers to the bone and/ or cementum surfaces were seen. chronic inflammatory cell infiltrate, dilatation of Summary and Conclusions 161 blood vessels and bone marrow cavities were frequently observed, in addition marked apical migration of attachment epithelium. Fibroblast cells showed definite signs of degeneration presented as marked shrinkage with degenerated organelles, the most extensively affected organelle in the cells of the tissues under investigation was the mitochondria, vacuolated cytoplasm and fatty infiltration.Resorption of bone was frequently encountered with a lot of osteoclasts in their howships lacunae. - group ӀӀI animals (recovery group):- The PDL showed nearly the same histological features of the control group (1.2) with slight condensation of the collagen fibers and fibroblasts of the PDL in addition to increased interstitial spaces full of blood vessels. The attachment epithelium of dentogingival junction showed marked improvement since there was no atrophic changes. Collagen fibers and fibroblast cells showed improvement in the condition of ultrasturctural features. There was obvious absence of osteoclasts and presence of osteoblasts and bone lining cells. . Masson’s trichrome stain results: - group 1.1 and 1.2 (control group):-PDL and the alveolar bone of the control group stained with Masson’s trichrome showed strongly positive reactivity of collagen fibers. 2- group ӀӀ animals (treated with AuNPs):PDL and the alveolar bone of group ӀӀ animals stained with Masson’s trichrome revealed weakly positive reactivity of collagen fibers.<- group ӀӀI animals (recovery group):- Summary and Conclusions162PDL and the alveolar bone of group ӀӀI animals revealed improvement in the arrangement and staining reactivity of the collagen fibers to Masson’s trichrome stain with moderately or strongly positive reaction of collagen fibers to Masson’s trichrome stain. Conclusions from the present