Studies On The Mechanism Of Toxic Effects Of Core Shell Structure Of Cadmium Quantum Dots At The Molecular And Cellular Levels

Quantum dots(Quantun QDs),as semiconductor nanomaterial,have some special surface properties due to the particularity of size.Quantum dots are widely studied and applied due to their superior photophysical properties,such as wide excitation spectra,narrow emission spectra,adjustable particle size,high fluorescence emission intensity and strong fluorescence stability.Quantum dot materials have shown good prospects in the fields of biomarkers,pharmaceutical chemistry,nonlinear optics,functional materials and chemical catalysis etc.However,with the wide applications of quantum dots,the chances of the exposure in production and life will also increase for people.Therefore,evaluating the potential physiological toxicity of quantum dots has become more and more important for human health.In view of these problems in the research on CdTe quantum dots which are synthesizedin the water phase with surface modification,eg a wide range distribution of particle size,agglomeration,single and rough,not rigorous surface modification,bad stability and high cytotoxicity,and the lack of the study on interaction with the protein in blood,we first study the interaction between MPA modified CdTe quantum dots synthesized in aqueous phase with hemoglobin,as an important protein which widely exists in blood,to supplement and support the existing research.In addition,we used MPA-CdSe/ZnS core-shell structure quantum dots coated by a non-toxic and tight stable ZnS shell with a very high bandwidth,good dispersibility,in high power microscope,to studyits toxic effects on the molecular and cellular level respectively.The main contents and conclusions are as follows:(1)MPA-CdTe quantum dots were synthesized by one pot method,and carried on the purification and vacuum drying to obtain solid quantum dots,and characterized by infrared spectroscopy,fluorescence emission spectroscopy,UV visible absorption spectroscopy,dynamic light scattering measurements and high-resolution transmission microscopy.Technical means to determine the synthesis and determination of its concentration.Aseries of experimental results showed that the MPA-CdTe QDs can be used to react with hemoglobin in the following experiments.(2)The effects of MPA-CdTe QDs on hemoglobin were studied under simulated physiological conditions by using isothermal titration calorimetry and multiple spectroscopic methods.We found that in the combination of hemoglobin and MPA-CdTe QDs,Vander Ed Ley and hydrogen bonds played a major role.The results showed that under the action of MPA-CdTe QDs,not only the intrinsic fluorescence of hemoglobin was quenched,but also the microenvironment of tyrosine and tryptophan residues,and the conformation of hemoglobin also changed dramatically,and the skeleton became extended and loose.However,the hemo in hemoglobin is still stable,indicating that the interaction between thm did not significantly inhibit the main physiological function of hemoglobin.Here,MPA-CdTe QDs is more likely to enter into the hemoglobin macromolecule rather than to gatheron its surface.(3)The MPA-CdSe/ZnS core shell quantum dots were characterized by fluorescence emission spectroscopy,UV Vis absorption spectroscopy and high power transmission electron microscopy.The results showed that the MPA-CdSe/ZnS core shell quantum dots have strong fluorescence emission intensity,small and symmetrical half peak width,the obvious diffraction aperture,the clear,stable and uniformly distributed lattice stripe,the stable core shell structure,good the dispersivity and the uniform particle size(4)Using isothermal titration calorimetry and various spectroscopic methods,we studied the interaction between MPA-CdSe/ZnS core shell quantum dots and the two kinds of oxidative kinase:catalase and superoxide dismutase,under simulated physiological conditions.The experimental results showed that the MPA-CdSe/ZnS nuclear shell structure quantum dots interacted with two kinds of oxidative stress kinase mainly through hydrophobic interaction.After the effects of MPA-CdSe/ZnS core-shell structure quantum dots the dots quenched intrinsic fluorescence of the two kinds of endogenous oxidative stress kinases,changed the microenvironment of tyrosine and tryptophan residues,and the molecular conformation also had a certain degree of unfolding in skeleton,but the physiological functions of the two kinds of oxidative kinase did not be significantly inhibited,but catalase molecule may be due to increasing exposure of the active center,its activity enhanced.(5)The primary hepatocytes of mice were selected as target cells.The cell viability,the activity of CAT and SOD and the change of MDA content in primary hepatocytes of mice were detected under the exposure of MPA-CdSe/ZnS core shell quantum dots.The results showed that the MPA-CdSe/ZnS quantum dots made the cell vitality of the primary liver of mice decrease slightly.The activity of CAT in primary hepatocytes of mice was only slightly changed,and the activity of SOD activity increased significantly.The content of MDA fluctuated upward and downward,but there was no significant difference.It is concluded that MPA-CdSe/ZnS core shell quantum dots induced oxidative stress in primary hepatocytes of mice,but have not yet caused severe oxidative stress damage to primary hepatocytes in mice.By using isothermal titration calorimetry and various spectroscopic methods,we firstly studied the interaction between MPA modified CdTe quantum dots in water and the widely existed and important hemoglobin in blood,which had complemented the existing research.In addition.In this paper,we also studied the toxic effects of the MPA-CdSe/ZnS nuclear shell structure quantum dots on the molecular and cellular levels.It provides a reference for the comprehensive evaluation of the toxicity of quantum dots,the synthesis of quantum dots and the rational use of quantum dots.