Aumento da concentração de selênio na síntese de pontos quânticos de CdSe: estratégia para o controle do estresse oxidativo no encéfalo do embrião de galinha

Abstract

Magic-sized quantum dots of CdSe (CdSe-MSQDs) have been widely used as fluorescent probes in biological systems. However, they may be cytotoxic depending on their size and composition. In order to avoid damage, new synthetic routes were proposed to control the oxidative damages caused by these nanoparticles. The aim of this work was to evaluate oxidative stress markers in chicken embryo encephalon exposed to CdSe-MSQDs synthesized with different concentrations of selenium. Sixty eggs were kept for ten days in a brooder with temperature and humidity control. At the ninth day, the eggs were divided in to six groups and received an injection in to the air chamber. The positive control group received 50 mM/egg of 2.20-Azobis (2- amidinopropane) dihydrochloride (AAPH), the negative control group received saline injection and the other groups received an injection containing CdSe solution at 4 different concentrations of selenium (0.4, 0.5, 0.8, 0.9 mM). After 24 hours, the eggs were opened and the encephalon was collected and homogenized to analyze the activity of the enzymes superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR) and catalase (CAT), reduced glutathione (GSH) quantification of lipid peroxidation (TBARS) and total antioxidant capacity (FRAP). In addition, analysis of the vascular density of the chorioallantoic membrane (CAM) was performed. Lipid peroxidation, enzyme activity of GPx, GR, CAT and SOD increased in the encephalon of the embryos exposed to CdSe-MSQDs with 0.4 mM of selenium compared to the control. There was also a decrease in total antioxidant capacity in this group. The amount of GSH decreased in the groups exposed to CdSe-MSQDs with 0.4 and 0.5 mM of selenium. The concentrations of 0.4 and 0.5 mM of selenium caused an expressive reduction in the vascular density of chicken embryos CAM. Our results showed that CdSe-MSQDs synthesized with low concentration (0.4 mM) of selenium affected the antioxidant defense system in the encephalon and the vascularization of CAM, whereas in higher concentrations of selenium, there was no damage. The higher concentrations of selenium decreased the amount of cadmium ions adsorbed on the surface of the CdSe-MSQDs, reducing their cytotoxic effect. These findings reinforce the importance of new synthetic routes for the production of nanomaterials with lower toxicity, for their safe use in biological systems.