الفهرس 
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Abstract
Toxoplasma gondii is an obligate intracellular protozoan parasite that causes opportunistic disease, particularly in immunocompromised individuals.
Nanotechnology is a collective term referring to technological developments on the nanometer scale. Nanoparticles have unique physicochemical properties, such as ultra-small size, large surface area to mass ratio, and high reactivity. Nanoparticles have collectively improved the bioavailability and drug properties.
In the present study Sixty-five laboratory-bred female Swiss Albino mice, Five mice were left as control negative (non-infected non-treated) while others sixty mice were experimentally infected orally with 20 cysts of avirulent ME49 strain of Toxoplasma gondii/mouse. Fifty days post-infection (pi), infected mice were divided into 4 groups (15 mice each); group 1: control group (infected non-treated); group 2: treated with Spiramycin (Rovamycin), group 3: treated with low-dose Au NPs; and group 4: treated with high-dose AuNPs. Treatment was administered orally for 10 days. Sixty days pi all groups were sacrificed and assessment of the effect of gold nanoparticles was achieved by parasitological, histopathological, ultrastructural, and biochemical study.
The present study showed a statistically very highly significant reduction in the mean cyst count and mean cyst size in brain, liver, and spleen of the infected mice treated with high dose gold nanoparticles (group4) compared to the infected non-treated control (group1) and infected mice treated with Spiramycin ( group2) (p-value 0.000). In addition, it showed a statistically significant reduction in the mean cyst count and a statistically non-significant reduction in the mean cyst size in the brain, liver, and spleen of the infected treated group with high dose AUNPs compared to the infected treated group with low dose AuNPs.
Histopathological examination of the brain, liver, and spleen tissues in this work showed that inflammatory reaction was diffuse and moderate to strong in control non treated mice (group1), mild to moderate in Spiramycin treated mice (group2), and minimal to mild in gold nano low dose (group3) and gold nano high dose (group4) treated mice., histopathological examination of the brain, liver and spleen tissues in this work furthermore detected Large-sized Toxoplasma cysts in non-treated mice (group1), the cysts were smaller in size in Spiramycin treated mice (group2). Few degenerated cysts were detected in gold nano low dose treated mice (group3) and they are almost absent in gold nano high dose treated mice (group4) and that was agreed with the results of light microscopic examination of impression smears of the same organs and groups.
Scanning electron microscopy (SEM) of the brain and liver tissue of mice showed Toxoplasma gondii cysts: with remarkable shrinkage, collapse, distortion and deep furrows in the wall in the gold nanoparticles treated mice group 3 and group 4 in comparison to the control non treated mice group 1 which showed a smooth regular surface of the cyst wall in both brain and liver cells and the Spiromycin treated group 2 which showed irregular ridges, protrusions, and pits on the surface of the cysts.
Transmission electron microscopy (TEM) of brain tissue of female mice infected with Toxoplasma gondii (ME49) showed Toxoplasma gondii cysts with extensive disintegration of cyst wall and vacuoles inside cysts in group 3 and degenerated cysts with large vacuoles inside in infected treated group with high dose AUNPs in comparison to partial disruption in the cyst wall in Spiromycin treated mice and intact cyst wall in control non treated mice.
The results revealed that there is a significant reduction in the mean value of ALT and AST in group 4 (gold nanoparticles high dose treated mice) in comparison to other groups (P < 0.05) which reflected the safety of their administration.
Conclusion:
At the end of this study, we can conclude that gold nanoparticles have a potent therapeutic effect, especially the high dose (800µg/kg/day) against experimental chronic toxoplasmosis (avirulent ME49 strain). Gold nanoparticles were able to induce a high significant diminution in the parasite burden. This was supported by the ultrastructural distortive effect of the drug on the cysts as proved by SEM and TEM studies. Gold nanoparticles caused a significant reduction of the elevated liver transaminases (ALT and AST).
Further studies are required to determine the therapeutic potential and efficacy of a drug delivery system, such as the loading of anti-Toxoplasma drugs on gold nanoparticles.