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Silicon-based quantum dots were intraperitoneally injected in individuals of Carassius auratus gibelio. Their effects on white muscle were investigated by following their distribution and impact on the antioxidative system. The GSH level significantly increased after 1 and 3 days of exposure by, respectively, 85.3 and 25.4%. Seven days later, GSH levels were similar to control concentrations. MDA concentration rose after three days by 46.9% and remained at the same level after 7 days. Protein thiol levels significantly decreased by 6.7 and 8.1% after 3 and 7 days, whereas advanced oxidation protein products increased by 12.7, respectively, 28.1% in the same time intervals. The protein reactive carbonyl groups were raised only after the first day of exposure and returned to the control level later on. SOD specific activity increased up to 48% after 7 days, while CAT activity increased by 328, 176, and 26% after 1, 3, and 7 days of treatment. GST specific activity was up-regulated by 87, 18, and 9%, while GR activity increased by 68, 34, and 9%. G6PD activity was up-regulated by 12, 22, and 50%, whereas GPx activity raised by 75 and 109% compared to control after, respectively, 1, 3, and 7 days. Our results suggest that oxidative stress induced by silicon-based quantum dots was not strong enough to cause permanent damage in the white muscle of crucian carp.

Silicon-based quantum dots were intraperitoneally injected in Carassius auratus gibelio specimens and, over one week, the effects on renal tissue were investigated by following their distribution and histological effects, as well as antioxidative system modifications. After three and seven days, detached epithelial cells from the basal lamina, dilated tubules and debris in the lumen of tubules were observed. At day 7, nephrogenesis was noticed. The reduced glutathione (GSH) concentration decreased in the first three days and started to rise later on. The superoxide dismutase (SOD) activity increased only after one week, whereas catalase (CAT) was up-regulated in a time-dependent manner. The activities of glutathione reductase (GR) and glutathione peroxidise (GPX) decreased dramatically by approximately 50% compared to control, whereas the glutathione-S-transferase (GST) and glucose-6-phosphate dehydrogenase (G6PDH) increased significantly after 3 and 7 days of treatment. Oxidative modifications of proteins and the time-dependent increase of Hsp70 expression were also registered. Our data suggest that silicon-based quantum dots induced oxidative stress followed by structural damages. However, renal tissue is capable of restoring its integrity by nephron development.

The use of quantum dots (QDs) in biomedical applications is limited due to their inherent toxicity caused by the heavy metal core of the particles. Consequently, silicon-based QDs are expected to display diminished toxicity. We investigated the in vivo effects induced by Si/SiO 2 QDs intraperitoneally injected in crucian carp liver. The QDs contained a crystalline Si core encased in a SiO 2 shell, with a size between 2.75 and 11.25 nm and possess intrinsic fluorescence (Ex 325 nm/Em ∼690 nm). Tissue fluorescence microscopy analysis revealed the presence of QDs in the liver for at least 2 weeks after injection. Although protein and lipid oxidative stress markers showed the onset of oxidative stress, the hepatic tissue exhibited significant antioxidant adaptations (increase of antioxidant enzymes, recovery of glutathione levels), sustained by the activation of Hsp30 and Hsp70 chaperoning proteins. The increased activity of cyclooxigenase-2 (COX-2) and matrix metalloproteinases (MMPs) support the idea that Si/SiO 2 QDs have a potential to induce inflammatory response, a scenario also indicated by the profile of Hsp60 and Hsp90 heat shock proteins. MMPs profile and the recovery of oxidative stress markers suggested a tissue remodelation phase after 3 weeks from QDs administration. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) interaction with living organisms is of central interest due to their various biological and medical applications. One of the most important mechanisms proposed for various silicon nanoparticle-mediated toxicity is oxidative stress. We investigated the basic processes of cellular damage by oxidative stress and tissue injury following QD accumulation in the gibel carp liver after intraperitoneal injection of a single dose of 2 mg/kg body weight Si/SiO2 QDs after 1, 3, and 7 days from their administration. QDs gradual accumulation was highlighted by fluorescence microscopy, and subsequent histological changes in the hepatic tissue were noted. After 1 and 3 days, QD-treated fish showed an increased number of macrophage clusters and fibrosis, while hepatocyte basophilia and isolated hepatolytic microlesions were observed only after substantial QDs accumulation in the liver parenchyma, at 7 days after IP injection. Induction of oxidative stress in fish liver was revealed by the formation of malondialdehyde and advanced oxidation protein products, as well as a decrease in protein thiol groups and reduced glutathione levels. The liver enzymatic antioxidant defense was modulated to maintain the redox status in response to the changes initiated by Si/SiO2 QDs. So, catalase and glutathione peroxidase activities were upregulated starting from the first day after injection, while the activity of superoxide dismutase increased only after 7 days. The oxidative damage that still occurred may impair the activity of more sensitive enzymes. A significant inhibition in glucose-6-phosphate dehydrogenase and glutathione-S -transferase activity was noted, while glutathione reductase remained unaltered. Taking into account that the reduced glutathione level had a deep decline and the level of lipid peroxidation products remained highly increased in the time interval we studied, it appears that the liver antioxidant defense of Carassius gibelio does not counteract the oxidative stress induced 7 days after silicon-based QDs exposure in an efficient manner. [ABSTRACT FROM AUTHOR]