Toxicity Assessment Of Photoluminescent Nanomaterials

Due to the growth of production and application, the probability of human contact with nanomaterials in occupational and environmental settings is increasing. With the decreasing of size, nanoparticles may have properties which do not exist in their microparticles. However, it is not fully understood whether nanoparticles may have adverse effects on human health. In this experiment, we selected quantum dots (QDs) and gold nanoclusters (Au NCs) for the toxicity assessment. After injection of the nanoparticles to mice, biodistribution, excretion, biocompatibility and oxidative stress were examined. Besides, the effect of nanoparticles on cytotoxicity in vitro was studied. The more detailed contents and results were shown as follows:1. We developed a method of atomic absorption spectrometry to quantitative analysis of Zn contents in the tissues of mice. The samples of tissues were digested with nitric acid and perchloric acid. The recovery of zinc standard in liver, lung, spleen, kidney, blood, and urine were between83.5%and118.9%, while recovery of the feces sample were73.4%and135.4%. We chose the blank liver sample to test the reproducibility of this method. The result of relative standard deviation (RSD) was1.75%.2. ZnS and ZnO QDs were synthesized via all-aqueous process with polyethylene glycol (PEG) chains on their surface, and their toxicity as well as biodistribution were evaluated. No hemolysis occurred at a high concentration of1600μg/mL in vitro hemolytic assay, which demonstrated that the QDs-PEG displayed good blood compatibility. Following intravenous administration at2,6, and20mg/kg of the QDs-PEG in mice, the biodistribution, excretion, and biocompatibility were characterized at1h,24h, and7d. Quantitative analysis results indicated that the biodistribution trend of ZnS QDs-PEG was similar to that of ZnO QDs-PEG. The QDs-PEG were mainly trapped in the lung and liver, and almost removed from blood within1h. QDs-PEG were primarily excreted in feces at the2and6mg/kg doses. Coefficients, hematology, blood biochemistry, and histopathology results indicated that the QDs-PEG were safe and biocompatible. 3. The hepatotoxicity including serum aminotransferases (ALT and AST), antioxidant enzymes (CAT, GSH-Px and SOD), lipid peroxidation and ultrastructure were evaluated after consecutive intravenous injection of ZnO QDs and QDs-PEG for7days in mice. Both ZnO QDs and QDs-PEG did not affect the coefficient of liver and the levels of serum aminotransferases. The antioxidant enzymes and lipid peroxidation had significant change after injecting5mg/kg ZnO QDs in24h, but all of these parameters returned to control levels in28d. ZnO QDs-PEG had less harmful effect on antioxidant enzymes and malondialdehyde than ZnO QDs at the same dose. According to the results of hepatocyte ultrastructure, both ZnO QDs and QDs-PEG were located in the mitochondrion and induced nuclear malformation in24h. The ultrastructure of hepatocyte was as normal as of the control group in28d and ZnO QDs were mainly trapped in the mitochondrion while ZnO QDs-PEG mainly accumulated in the lysosomes.4. Doped quantum dots are useful tool in biological labeling and drug delivery due to their longer dopant emission lifetime and potentially lower cytotoxicity. We synthesized Mn-doped ZnS QDs and investigated the hepatotoxicity induced by repeated intravenous injection to mice in this study. The body weight had no change all over the treated and post-injection periods. Mn-doped ZnS QDs and QDs-PEG did not disturb the coefficient of liver and the levels of serum aminotransferases in both24h and28d. The antioxidant enzymes activity as well as malondialdehyde (MDA) had no change in the entire experiment, indicating that Mn-doped ZnS QDs and QDs-PEG could not induce oxidative stress in the liver of mice. According to the hepatic cell ultrastructure, the hepatocyte of Mn-doped ZnS QDs and QDs-PEG treated groups were as normal as of the control group, and most of Mn-doped ZnS QDs were distributed in the mitochondrion.5. We synthesized water-soluble fluorescent gold nanoclusters (Au NCs) stabilized with dihydrolipoic acid (DHLA). The cytotoxicity of DHLA-stabilized Au NCs was then assessed in the normal human hepatic cell line (L02) and the human hepatoma cell line (HepG2) at different exposure times. Cell viability was normal in both cell lines at24and48h, however, the growth of HepG2cells was significantly inhibited at72h. The change in lactate dehydrogenase (LDH) level was strongly correlated with cell viability after72h incubation with DHLA-stabilized Au NCs, and the increase in cellular reactive oxygen species (ROS) might be related to the decrease in cell viability. Growth inhibition of HepG2cells was possibly due to difficultly passing the check point between G1phase and S phase.