الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The preservation of important vital structures that surround the cancer cells of head and neck region is a big challenge in treatment planes of these cancers. Recent studies focus on providing an accurate treatment to cancer cells and fewer amounts of damages to the surrounding structures. Gold nanoparticles have unique properties which depend on its different characterization criteria. Also, GNPs were found to have cytotoxic effect on some cancer cells including squamous cell carcinoma of oral cavity and larynx.
The current study aimed to investigate the effect of changing the shape of GNPs on its cytotoxicity on Hep-2 squamous cell carcinoma cells, to investigate the effect of different concentrations of GNPs on its cytotoxicity on Hep-2 squamous cell carcinoma cells line and to correlate the effect of different shapes and concentrations of GNPs on its cytotoxicity on Hep-2 squamous cell carcinoma cells line.
In this study, we have employed assays to evaluate the cellular uptake and cytotoxicity of GNPs in Hep-2 cell line. Our study includes two different types of GNPs which have two morphologies: spherical shape with average size ~ 20 - 25 nm and rod shape with aspect ratio 2.84.
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To answer the question of cytotoxicity detailed assays are used: cell viability, histopathological pictures, anti-oxidant test, image morphometric analysis and flow cytometry assay.
Results of the present study revealed that the GNPs have cytotoxic effect on Hep-2 cells after 24 hours, GNRs are more toxic than GNSs and the viability percentages decreased with increasing concentrations of GNPs after 24 hours.
Histopathological pictures showed that the criteria of necrosis were prominent at pre IC50 concentrations of GNSs and GNRs independently. The apoptotic changes increase with increasing concentration from pre IC50 to IC50 of GNSs and GNRs independently. At the post IC50 of GNRs the necrotic changes increased when compared to the IC50 of GNSs.
According to the GSH level, we found that the mean GSH levels decreased in cells after treated by GNPs for 24 hours when compared to control untreated Hep-2 cells. Therefore, these results propose that oxidative stress is a part in GNPs induced cytotoxicity.
Statistical analysis of the present study regarding to the GNSs showed a highly significant decrease of the mean NAF of Hep-2 cells treated with GNSs when compared with control cells after 24 hours (p<0.000). Increasing in the concentrations of GNSs from pre IC50 to IC50 to post IC50 showed a statistical
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insignificant decrease in the mean value of NAF after 24 hours (p=1).
Regarding to GNRs, the statistical analysis also showed a highly significant decrease of the mean NAF of Hep-2 cells treated with GNRs when compared with control cells after 24 hours (p<0.000). Statistical examinations revealed that there was a statistical significant decrease in the mean value of NAF after 24 hours from pre IC50 to IC50 concentrations of GNRs (p<0.000).
But there was a statistical insignificant increase in the mean of value of NAF from IC50 to post IC50 concentration of GNRs after 24 hours (p=.441).
The data obtained from FSC histograms showed that there was shifting in the curve of Hep-2 cells treated by GNPs to the left side of x-axis when compared to the control cells after 24 hours. This means that there was a reduction in cell size of cells treated by GNPs, consistent with apoptosis.
The FSC histograms revealed that there was the reduction in cell size increased by increasing concentrations of GNSs. The cell size decreased with increasing concentrations of GNRs from pre IC50 to IC50. Regarding to GNRs, there was an increasing in cell size from IC50 to post IC50 which indicated that there was a decreasing in apoptosis with increasing concentration from IC50 to post IC50.
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Flow cytometry data denoted that there was an increasing percentage of cells at S-phase followed by a decreasing at G2-phase in cells treated by GNPs when compared to control cells after 24 hours.
This reduction in percentages of cells can be explained by effect of GNPs on cells as the GNPs induce DNA damages by their effects on mitochondria or/and by facilitating formation of ROS. Thus, GNPs suppress the DNA synthesis at S-phase.