Biological Effects And Mechanism Study Of Copper Nanoparticles In Bombyx Mori

With the gaining popularity of nanomaterials, an increasing number of nanoproducts are used in our daily life, and as a result, the opportunities of nanomaterials exposure to human are greatly increased. As a kind of typical metal nanomaterials, copper nanoparticles(Cu NPs) have distinctive physical and chemical properties and they have been widely applied to various fields. Given such wide use of Cu NPs, the biosecurity of Cu NPs has attracted people's attention. At present, the toxicological study of Cu NPs is scanty and the toxic mechanism is still unclear. Furthermore, most toxicity tests of Cu NPs are based on senior animal which is expensive and highly ethical and moral controversy. In order to solve these existing problems and provide theoretical basis for the biological safety evaluation of Cu NPs, searching for a model animal which is low cost, less controversial and responsive to nanomaterials, is crucially important to the studies of biological toxicity on Cu NPs.In this thesis, the 3-day-old larvae of fifth-instar Bombyx mori was used as experimental models, and the toxic effects and mechanism of Cu NPs to it was investigated following the exposure to the dose of 200 ?g per larvae(200 ?g/T). The Cu NPs suspension was exposed to the Bombyx mori by injecting through the second pleopod. The main results in this thesis were summarized as follows:1. Different concentrations of 20 nm Cu NPs suspension were injected to the Bombyx mori. The calculated result of the exposure experiment showed that the 48 h LD50 of Cu NPs to Bombyx mori was 196.05?g/T, and the 95% confidence intervals was 145.85?230.15 5?g/T. The exposure of Cu NPs inhibited the growth, affected the appetite, which also brought some damages to the tissues of Bombyx mori. Furthermore, the toxicity Cu NPs in exposed Bombyx mori was dose-dependent and time-dependent.2. A new method for detecting the concentration of Cu in the tissue of Bombyx mori using microwave digestion-inductively coupled plasma mass spectrometry was established. The result demonstrated that the correlation coefficients for Cu were 0.99945 and 0.99969 in the control and treatment groups, respectively. The recovery of Cu element was between 101% and 106%, and the relative standard deviations(RSD) was less than 3.22%. The result also indicated that, compared with the blank group, the concentration of Cu in the tissues exposed to Cu NPs was significantly increased(p<0.05). As the changes of the Cu concentration in the fat body, midgut and trachea were relatively larger, these organs may be the main target organs of Cu NPs toxicity.3. The pathological changes of Bombyx mori tissues and the morphology of Cu NPs in tissues were investigated by paraffin section technique, TEM and EDS. The results show that, the Cu NPs were present in the tissues with the pristine NPs form, which not only destroyed the defensive barrier and cause tissue injury, but also produced a certain poison to the histiocyte. The result also showed that with the Cu NPs entered into the histiocyte, the NPs will be surrounded by membrane. But the composition and functional mechanism of the membrane were still unclear and need further study.4. The exposure of Cu NPs caused oxidative tissue damage in the Bombyx mori. Compared with the control group, the level of ROS in the tissues was significantly increased(p<0.05). The level of oxidative damage marker 8-OHd G and MDA in tissues, generated by oxidative DNA damage and lipid peroxidation respectively, were significantly increased(p<0.05). The antioxidase CAT and SOD in the tissues were significantly inhibited by the exposure of Cu NPs(p<0.05), and as a result, the antioxidant system of Bombyx mori was severely destroyed. The level of c AMP in different tissues was significantly inhibited(p<0.05).5. The exposure of Cu NPs could effect the expression of inflammatory cytokines in histiocyte and destroy the immune mechanism of Bombyx mori, and as a result,the tissues were severe damaged. The exposure of Cu NPs significantly increased the expression levels of Cys C, NF-?B and Fas(p<0.05) in the tissues and blood, and significantly inhibited the expression levels of Ig and c AMP(p<0.05)..