Reproductive Toxicity Induced By Cadmium Telluride Quantum Dots And The Mechanism Determined In Bombyx Mori

Quantum dots(QDs) have shown promising potentials as novel biomedical imaging agents. However, biosafety assessment of QDs is still a controversial issue and remains demonstrated major challenge. The long-term reproductive toxicity lacks of systematic and in-depth study. The invertebrate model organism, Bombyx mori, was selected to determine the reproductive toxicity of Cd Te QDs(With diameter of 2-3nm, excitation wavelength of 490 nm, emission wavelength of 530 nm).We also explored the mechanisms of the damage to gonads after QDs exposure. In particular, whether QDs decorated with glycine or alanine have a positive impact on reducing the toxicity or not was determined. The results were as follows:1 Cd Te QDs can directly entered gonads by dorsal intravenous injection in B.moriWe can detect the fluorescence of QDs in testis and ovary after being exposed by a dose of 0.32 nmol QDs for 24 h and 48 h.When the dose of QDs increased to 0.64 nmol, the QDs, QDs-Ala and QDs-Gly can be observed in testis and ovary after 12 h. However, the green fluorescence intensity of QDs decorated with amino acid was weak. And the amount of gonads showed weak fluorescence was more than QDs, which implied that amino acid surface modification can reduce the amount of QDs into the gonad. On the other hand, the characteristic fluorescence display, whether QDs decorated with amino acid or not, its transfer and accumulation in the testis are more than the ovary. Which suggested that there exsited the gender difference in the reproductive toxicity of QDs.2 Cd Te QDs exposure influenced on spawn and fertilizationMating tests showed that, after female larvae and male larvae were both exposured to QDs, fertilized egg rate was zero, and ovarian remnant eggs rate was as high as 48%, while the control group, the average fertilization rate was 95%, and the remaining egg rate was only 1%. After female larvae being exposured to QDs, fertilization rate only decreased 9%, while the remnant eggs rate was as high as 20%. After male larvae being exposured to QDs, even mated with normal female, fertilized egg rate was only 49+12%. QDs had very strongmale germ cell toxicity, the toxicity on female concentrated on influencing the behavior of oviposition. In the mating experiment, adverse effects of QDs-Ala and QDs-Gly were less than QDs, showing decorated with amino acid can reduce the reproductive toxicity of QDs.3 Cd Te QDs exposure influenced on germ cell developmentHE staining of the gonads after being exposured for 120 h showed that the development of testis and ovary was delayed. DAPI staining showed that testis generative cell nuclei appeared serious injury, ovarian cell nuclei also had certain morphological abnormalities. Seminal cells in vitro were cultured for 168 h of incubation after being exposured to QDs for 12 h, 24 h and 72 h. The QDs group spermatocyst formation and development of sperm bundles than that of the control were reduced by 33%, 54% and 25%, while QDs-Ala group in reduced 16%, 43% and 5%, QDs-Gly group reduced 33%, 52% and 16%. Compared with the control group, QDs group spermatocyst damage rate increased by 51%, 53% and 45% respectively. QDs-Ala group increased by only 10%, 13% and 13%, QDs-Gly group increased 19%, 30% and 11%. The whole process of dynamic culture showed that QDs exposure experience in vivo significant induced the damage of seminal cells development, and QDs-Ala showed better effect of reducing toxicity.4 Cd Te QDs reproductive toxicity is regulated and controlled by a variety of molecular mechanismAfter exposure to QDs for 12-72 h, QDs can break the gonads’ outer membrane, and induced spermary cells, ovariole membrane and ovariole cells to produce lots of reactive oxygen species(ROS). Further mitochondrial structure was destructed, and the key gene Dronc of caspase apoptotic pathway was up-regulated expression. At the same time, lysosome increased associating with autophagy, and lysosomal permeability changed. The expression of gene Atg6 and Atg8 were up-regulatedly associated with autophagy. QDs might induce early germ cell death or deformity by the composite mechanism of mitochondrial and lysosomal apoptosis or autophagy pathways.