The Developmental Toxicity Of CdSe/Zns Quantum Dots In Zebrafish In Vivo

The science in nanometer scale, which is jusaposed the information science and the bioscience, is one of the three most important research fields in the 21 century. In the past 30 years, the nanoscience had a rapid development. The application and basic research of nanomaterials in many medicine-related fields has also made significant progress. However, in the course of the study, there are still many problems to be solved, and therefore much attention has been paid to the biological security of nanoparticle materials by investigators all over the world. In the present, the achievements that have been made in nanotoxicity are basically based on systems in vitro. However, the study in vitro developed tardily because of the limitations of many factors such as expensive and time-consuming and so on. Thus now, there are many problems and challenges to establish systemic, all-sided methods for nanotoxicology in vivo.Zebrafish(Danio Rerio) is one of the important model vertebrates in the life sciences, and is widely used in toxicological studies. The zebrafish is responsive to water pollution and toxic substances. So it is widely used for water quality monitoring. And zebrafish has many advantages, such as large amount of ovulation, rapid development, transparent embryo which can rapidly absorb the small molecules and its highly similar genome to human, which has a broad prospects for application in the evaluation of drug toxicity.In this study, we combined the zebrafish with nanomaterials, two research focus in recent years, made full use of zebrafish as a unique advantage of the life science research model organisms, designed the methods of vascular injection, gavage, yolk sac injection(including different developmental period of zebrafish), exposure to nanoparticles (including different developmental period of zebrafish) and compared their advantages and disadvantages. Ultimately, we had identified yolk sac injection administration at 24 hours after fertilization to evaluate the toxicity of nanometer-scale quantum dots. First, we Determined the half-lethal dose(LD50) of quantum dots. Then we observed and tracked its movement and distribution in vivo by fluorescence microscopy. Finally, we found that quantum dots spread throughout the body through the blood circulation system and the aggregation phenomenon existed in the eye and surrounding tissue. Phototaxis experiments show that the eye did not cause serious injury such as blindness, and more evidence is needed to ascertain whether quantum dots caused other effects on the eyes. We also compared the toxicity of quantum dots which had the same chemical composition (CdSe/ZnS) before and after PEG modification and particle size, and we found that not PEG-modified quantum dot had greater toxicity. This result proved that the heavy metals composition in quantum dot had a greater impact on its toxicity. We used gene chip to conduct a comprehensive analysis of the toxic effects of the quantum dots, and reverse transcription real-time quantitative PCR(RT-qPCR) on the part of the abnormal expression of genes for authentication, to investigate the impact of the abnormal signaling pathways and protein expression. Then its toxicity mechanism in vivo can be interpreted preliminarily.The significance of this experiment is to want to find and establish a comprehensive, efficient and effective method to assess nano-particle toxicity studies in vivo, and analyse the impact and mechanisms of toxicity of quantum dots in vivo, and make an objective assessment of the possibility that we use the quantum dot as a drug carrier or labeled compounds at the same time.