الفهرس 
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Abstract
Nanotechnology is an advanced non-conventional technique that includes nanoscale-oriented science and engineering. It includes particulate matter of a fraction of a billionth of a meter or as determined by the National Nanotechnology Initiative in approximate sizes ranging from 1 to 100 nanometers. This technique has many applications, specifically in the medical field known as Nanomedicine.
In recent years, Nanoscale materials have become the focus of research that is of interest to most countries around the world due to the potential impact of Nanoscale materials in the treatment and diagnosis of many diseases, especially cancer, which presupposes a promising future for nanotechnology in multiple medical applications.
In the field of tumor treatment, radiation therapy is still the main and most effective method of treatment of tumors, especially cancer. Recent techniques include the use of X-rays in the Mega volts range to avoid damage to the surface of the skin, and the intensity modulated radiation therapy to focus on giving the dose better within the size of the tumor without affecting the healthy tissue.
In modern radiotherapy, X-rays of linear accelerators in the energy range of mega- volts have been increasingly used to replace x-rays in the range in kilovolts to treat deep subcutaneous tumors because they provide clear advantages in terms of dose determination within tumor size and dose reduction to the skin surface due to the high penetration capability of high-energy X-rays.
In recent years, Nanoparticles have been widely used in the field of radiotherapy because of their micro-size and compatibility with living tissues, and the ease of chemical modification in terms of the increasing number of reports and researches in this field, in which the Arab Republic of Egypt contributed a lot to the Egyptian scientist Dr. Mustafa El Sayed.
The aim of the present study was to study the effect of Gold Nanoparticles as a radiosensitizer for x-rays- irradiated mice bearing Ehrlich ascites carcinoma.
To achieve this aim Gold Nanoparticles were prepared by reduction of hydrogen tetrachloroaurate (HAuCl4.3H2O) by 1% trisodium citrate. The prepared Nanoparticles were characterized in terms of shape by transmission electron microscope, Size and charge by zeta analyzer and optical properties by scanning the plasmonic absorption band using uv-visible spectrophotometer.
For the evaluation of the effect of prepared Gold Nanoparticles as a radiosensitizer in vivo, sixty mice implanted with Ehrlich ascites carcinoma cells were divided into six main groups, each group consisting of 10 mice:
group I : Control untreated group and injected with saline with no irradiation.
group II : Injected with saline and irradiated with 6 Gy X-ray radiation.
group III : Injected with saline and irradiated with 2 Gy X-ray radiation for three times day by day.
group IV : Injected with 10 nm Gold Nanoparticles with no irradiation.
group V : Injected with 10 nm Gold Nanoparticles and irradiated with 6 Gy X-ray radiation.
group VI : Injected with 10 nm Gold Nanoparticles and irradiated with 2 Gy X-ray radiation for three times day by day.
To study the radiosensitizing effect of X-rays exposure mice bearing Ehrlich Ascites Carcinoma on the tumor in different animal groups, the following parameters were estimated: tumor volume (mm3), tumor volume ratio (TVR), inhibition ratio of tumor, mice survival time and life span and determination of total antioxidant (TAC) and malondialdehyde (MDA). Animal weight, white blood cell counts and liver enzymes activity were assayed as general markers of toxicity.
Our results can be summarized as follow:
- GNPs around 10.4 nm were obtained by chemical reduction method with sodium citrate. The zeta potential of prepared Gold Nanoparticles was -32.2 mv ± 2.15 with 1.41 mS/cm conductivity. The plasmon absorption of prepared GNPs was clearly visible and its maximum absorption peak was at 522 nm.
- There were no significant difference in tumor volume between animals irradiated with 6 Gy X-ray once and those irradiated with 2 Gy X-ray for three times. Animals injected with Gold Nanoparticles prior to 6 and 2 Gy X-ray irradiation showed significant reduction in tumor volume compared with animals irradiated with 6 and 2 Gy X-ray only after 3 and 7 days.
- The mean tumor volume of animals irradiated with 2 Gy X-ray after 7 days of irradiation was 1.99 times greater than that after 24 hours post irradiation with tumor inhibition ratio of 56.5 compared with control group, while the mean tumor volume of animals injected with Gold Nanoparticles prior to 2 Gy X-ray after 7 days of irradiation was 1.41 times greater than that after 24 hours post irradiation with tumor inhibition ratio of 76.5 compared with control group.
- The mean survival time of mice injected intratumoral with GNPs and irradiated with 6Gy and 2Gy (three times) X-ray were significantly higher than that of control group, while no other groups showed significant difference.
- Animals injected with GNPs prior to 6 Gy X-ray irradiation showed significant elevated concentration of MDA after 1 day post irradiation compared with control group with no significant difference after 3 and 7 days post irradiation. Animals injected with GNPs prior to 2 Gy X-ray irradiation (three times) showed non-significant difference in concentration of MDA after 1, 3 and 7 days post irradiation compared with control group, but was significantly lower at 3 and 7 days post irradiation compared with its corresponding group that did not injected with GNPs (GpIII).
- Animals injected with GNPs prior to 6 Gy X-ray irradiation showed significant reduction in TAC levels after 1 day post irradiation compared with control group with no significant difference after 3 and 7 days post irradiation. Animals injected with GNPs prior to 2 Gy X-ray irradiation (three times) showed non-significant difference in TAC levels after 1, 3 and 7 days post irradiation compared with control group, but was significantly higher at 3 and 7 days post irradiation compared with its corresponding group that did not injected with GNPs (GpIII).
- All animals were free of toxic clinical signs throughout the experiment period of 7 days. Mice injected with GNPs intratumorally prior to X-ray irradiation did not cause body weight changes compared with the control group during 7 days post irradition.
- Animals injected intratumoral with GNPs prior to irradiation with 6 Gy and 2 Gy (three times) of X-ray showed significant reduction in WBCs count compared with control group but higher than their corresponding groups that did not injected with GNPs.