The Research Of The Toxicity And Damage Mechanism Induced By Silica Nanorattle In Vivo

With the rapid development and extensive application of mesoporous silica nanoparticles (MSN), especially the potential biomedical applications for diagnosis and therapy of cancer, the toxicity of MSNs have received more and more attention. However, the biosafety and biodistribution caused by MSN have not been sufficiently understood. Therefore, in this dissertation, we choose silica nanorattle as a model particle to investigate the toxicity induced by them in vivo. The biodistribution and the injury mechanism have also been studied. This work provides a significant basis of SN for the potential application in the biomedical field. The detailed works are summarized as following:1 The effect of the particle sizes on the acute toxicity of SNIn order to select the low toxicity or nontoxicity of the nanoparticles, the acute toxicity of SN with different sizes was examined. The median lethal dose (LD50), clinical feature, necropsy and blood tests were measured to evaluate the effects of different sizes of SN with the diameter of 60, 110 and 260 nm (SN-60, SN-110 and SN-260). The LD50 of SN-60 was less than 200 mg/kg, and the LD50 of SN-110 and SN-260 nm were more than 400 mg/kg. Compared with the control groups, the mice treated with SN-60 at the dose of 400 mg/kg showed many abnormalities including the decrease of activity, crouching, hunching and even death. The examinations of necropsy showed that the SN-60 caused the hemorrhages to the gastrointestinal tract, mesenteric lymph nodes and bladder. And a large area of spotty necrosis appeared in the liver induced by SN-60 at 400 mg/kg. These results demonstrated that SN-60 showed more obvious acute toxicity than that of SN-110 and SN-260. Based on above investigations, SN-110 was selected for further studies.2 The acute toxicity and the mechanism of injury in the liver induced by SNTo examine the acute toxicity of SN-110 nm, clinical manifestations, blood count, blood chemistry and histopathological morphology of the mice injected intravenously with SN-100 nm at the does of 40,80,240 mg/kg were investigated systematically. Blood chemistry tests shown that the levels of ALT and AST in the mice treated with 240 mg/kg SN-110 increased significantly as compared with those of the control group (p<0.05). The pathologic examination showed that lymphocytic infiltration in the liver was observed in SN injected at 240 mg/kg. In order to study the damage mechanism induced by SN, the contents of anti-oxidation indexes including superoxideenzyme (SOD), glutathione (GSH), catalase (CAT) and the oxidation product (MDA) were detected. The results show that the activity of SOD induced by SN in the liver decreased significantly, the other indicators changed unremarkably. This study revealed that liver was the target organ of the SN. It also can be concluded that activity of SOD played an important role in liver injury caused by SN.3 The subacute toxicity and the mechanism of injury in the liver induced by SNIn order to investigate the subacute toxicity and mechanism of injury caused to the liver induced by SN-110 nm,20 female mice divided into 4 groups were intraperitoneally injected with SN suspension in sterile 5% glucose at 10,25 and 50 mg/kg. And the control group was injected with equal-volume 5% glucose. Body weight, coefficients of tissues, clinical manifestations, blood biochemistry assay, histopathological examinations, masson’s trichrome stain of tissues and hydroxyproline assay were performed. The results shown that Alanine aminotransferase (ALT) level in serum and hepatic hydroxyproline contents were significantly increased in SN injected at 50 mg/kg compared with that of the control group. The pathologic examination showed that lymphocytic infiltration, suspected silicotic nodular like lesions and hepatocyte fibrosis in the liver were observed in SN injected at 25 and 50 mg/kg. The mechanism of the subacute injury in the liver induced by SN was investigated by the immunohistochemistry, transmission electron microscopy (TEM) and the measurements of proinflammatory cytokines. The expression value of 8-OHdG and CD68 in Kupffer cells, and the levels of inflammatory cytokine IL-1βand TNF-αin serum were significantly increased in the mice treated SN at 25 and 50 mg/kg, while no elevation was observed in the mice treated with SN at 10 mg/kg. TEM found that a large number of SN existed in the cells of the suspected silicotic nodular like lesions. The results indicated that the target organ of the subacute toxicity of SN was the liver and Kupffer cells played an important role in the liver damage caused by SN after intraperitoneally administration.4 The biotransport and excretion of SN in vivo through intravenous injectionIn order to reveal the relationship between the biotransport and toxicity of SN in the body, a total of 12 female ICR mice were allocated to two groups.9 1CR mice were intravenously administrated with SN-FITC suspension in sterile 5% glucose at 80 mg/kg, and the remaining mice were injected with equal-volume 5% glucose. Then they were slaughtered at 24 h,7 d and 28 d. Fluorescence microscopy, and transmission electron microscopy (TEM) were undertaken to investigate the distribution, transport and excretion of SN in the body after intravenous administration. The results of fluorescence microscopy and ICP-OES showed that the injected SN in the bloodstream reached the liver and spleen quickly. The distribution of SN in the liver and spleen changed over time. The observation of SN in the feces and urine by TEM found that SN was mainly excreted form the mice through the feces.In conclusion, the toxicities of the different sizes of SN provide a basis for selecting the nano-particles of appropriate size in biomedical applications. The study of the toxicity and metabolism of SN showed that SN had a good biocompatibility. But SN injected in high dose or repeatedly injected can cause damages to the liver. Therefore, not only a satisfactory therapeutic efficacy can be obtained, but also the side effects can be avoided by the control the dose of administration and numbers of injections of SN. The study of damage mechanism caused to liver induced by SN provides the guidelines for the prevention and treatment of side effects. And this study provides important foundation of safety evaluation for the investigation of nano-materials.