Exploring In Vivo Pulmonary and Splenic Toxicity Profiles of Silicon Quantum Dots in Mice.

Silicon-based quantum dots (SiQDs) represent a special class of nanoparticles due to their low toxicity and easily modifiable surface properties. For this reason, they are used in applications such as bioimaging, fluorescent labeling, drug delivery, protein detection techniques, and tissue engineering despite a serious lack of information on possible in vivo effects. The present study aimed to characterize and evaluate the in vivo toxicity of SiQDs obtained by laser ablation in the lung and spleen of mice. The particles were administered in three different doses (1, 10, and 100 mg QDs/kg of body weight) by intravenous injection into the caudal vein of Swiss mice. After 1, 6, 24, and 72 h, the animals were euthanized, and the lung and spleen tissues were harvested for the evaluation of antioxidant enzyme activity, lipid peroxidation, protein expression, and epigenetic and morphological changes. The obtained results highlighted a low toxicity in pulmonary and splenic tissues for concentrations up to 10 mg SiQDs/kg body, demonstrated by biochemical and histopathological analysis. Therefore, our study brings new experimental evidence on the biocompatibility of this type of QD, suggesting the possibility of expanding research on the biomedical applications of SiQDs.

In Vivo Assessment of Hepatic and Kidney Toxicity Induced by Silicon Quantum Dots in Mice.

In the last decade, silicon-based quantum dots (SiQDs) have attracted the attention of researchers due to their unique properties for which they are used in medical applications and in vivo imaging. Detection of cytotoxic effects in vivo is essential for understanding the mechanisms of toxicity, a mandatory step before their administration to human subjects. In this context, we aimed to evaluate the in vivo hepatic and renal acute toxicity of SiQDs obtained by laser ablation. The nanoparticles were administrated at different doses (0, 1, 10, and 100 mg of QDs/kg of body weight) by intravenous injection into the caudal vein of Swiss mice. After 1, 6, 24, and 72 h, the animals were euthanatized, and liver and kidney tissues were used in further toxicity tests. The time- and dose-dependent effects of SiQDs on the antioxidant defense system of mice liver and kidney were investigated by quantifying the activity of antioxidant enzymes (catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase, and glutathione S-transferase) in correlation with the morphological changes and inflammatory status in the liver and kidneys. The results showed a decrease in the activities of antioxidant enzymes and histopathological changes, except for superoxide dismutase, in which no significant changes were registered compared with the control. Furthermore, the immunohistochemical expression of TNF-α was significant at doses over 10 mg of QDs/kg of body weight and were still evident at 72 h after administration. Our results showed that doses under 10 mg of SiQDs/kg of b.w. did not induce hepatic and renal toxicity, providing useful information for further clinical trials.

Hydroxyapatite-bioglass nanocomposites: Structural, mechanical, and biological aspects.

This research work focuses on the fabrication and study of a series of nanocomposites consisting of two types of hydroxyapatite (HA), obtained by precipitate (HAP) and sol-gel (HAG) methods, and a boro-silico-phosphate bioglass. The microstructure and chemical, mechanical, and biological properties as functions of three factors, namely (i) the type of hydroxyapatite, (ii) glass content, and (iii) sintering temperature, were investigated. It was found that all of these factors affect the final composition and microstructure, especially, porosity, which shows significantly lower values for HAP-based composites than for HAG-based ones and higher values for higher glass content. This, in turn, has an impact on the microhardness, which exhibits a strong correlation with porosity, as well as on the mineralization capability and cell viability due to the different dissolution rate.

New Insights into the Cell Death Signaling Pathways Triggered by Long-Term Exposure to Silicon-Based Quantum Dots in Human Lung Fibroblasts.

This report is the first research study that aims to explore the molecular mechanisms involved in the in vitro pulmonary cytotoxicity triggered by long-term exposure to silicon-based quantum dots (QDs). Human lung fibroblasts (MRC-5 cell line) were exposed to 5 µg/mL silicon-based QDs for 5 weeks and the concentration was increased up to 40 µg/mL QDs during the next 4 weeks. Cell viability and population doubling level were calculated based on Trypan blue staining. The expression levels of proteins were established by Western blotting and the telomeres' length was determined through Southern blotting. Prolonged exposure of lung fibroblasts to QDs reduced the cell viability by 10% compared to untreated cells. The level of p53 and apoptosis-inducing factor (AIF) expression increased during the exposure, the peak intensity being registered after the seventh week. The expressions of autophagy-related proteins, Beclin-1 and LC-3, were higher compared to untreated cells. Regarding the protein expression of Nrf-2, a progressive decrease was noticed, suggesting the downregulation of a cytoprotective response to oxidative stress. In contrast, the heat shock proteins' (HSPs) expression was increased or maintained near the control level during QDs exposure in order to promote cell survival. Furthermore, the telomeres' length was not reduced during this exposure, indicating that QDs did not induce cellular senescence. In conclusion, our study shows that silicon-based QDs triggered the activation of apoptotic and autophagy pathways and downregulation of survival signaling molecules as an adaptive response to cellular stress which was not associated with telomeres shortening.

Analyzing the Interaction between Two Different Types of Nanoparticles and Serum Albumin.

Two different types of nanoparticles (silicon dioxide and titanium dioxide) were selected within this study in order to analyze the interaction with bovine and human serum albumin. These particles were characterized by transmission and scanning electron microscopy (TEM and SEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDXS). In addition, the hydrodynamic size and the zeta potential were measured for all these nanoparticles. The serum proteins were incubated with the nanoparticles for up to one hour, and the albumin adsorption on the particle surface was investigated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The effect induced on the secondary structure of proteins was analyzed by Fourier transform infrared spectroscopy (FTIR). The results showed that albumin adsorbed on the surface of both types of nanoparticles, but in different quantities. In addition, we noticed different changes in the structure of albumin depending on the physicochemical properties of each type of particle tested. In conclusion, our study provides a comparative analysis between the different characteristics of nanoparticles and the protein corona formed on the particle surface and effects induced on protein structure in order to direct the development of "safe-by-design" nanoparticles, as their demands for research and applications continue to increase.