Interactions Of The Thiol Capped Cdte Quantum Dots With Some Proteins And Its Cellular Toxicity

1. An overview of the fundamentally physical properties of quantum dots (QDs), the organic-phase and aqueous-phase synthesis methods as well as the surface modification methods were summarized first; then the status and progress of QDs applications in the fields of analytical science and biomedicine, and their toxicological effects were introduced briefly. On this basis, we provided the research scheme of this paper.2. By using N-acetyl-L-cysteine (NAC) or mercaptopropionic acid (MPA) as stabilizer, the high quality cadmium telluride (CdTe) quantum dots with different particle sizes were prepared via hydrothermal method, respectively. The NAC/MPA-CdTe QDs are characterized by UV-Vis absorption spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy and transmission electron microscopy. The results show that the quantum dot size distribution is homogeneous, the UV absorption spectrum is broad and continuous, the fluorescence emission peaks are narrow and symmetric, and the emission range covers almost the entire visible region (480-760nm). By changing the reaction time, the modulation of the fluorescent emission wavelength of quantum dots is achieved.3. The interactions of CdTe quantum dots and CdTe/CdS core-shell quantum dots with cytochrome c (Cyt c), and CdTe quantum dots with bovine serum albumin (BSA) under physiological conditions were investigated by using fluorescence spectroscopy, respectively. We found that Cyt c has a significant fluorescence quenching effect on the quantum dots with different sizes; however, the introducing of BSA markedly enhanced the fluorescence of quantum dots. And quantum dots not only have obvious fluorescent quenching effect on BSA, but also make the conformation of BSA change. The possible mechanisms of the fluorescence enhancement effect of BSA on the quantum dots and the fluorescence quenching effect of Cyt c on them were discussed. The above study may lay a foundation for the further research on the interactions of quantum dots with proteins in live cells.4. The interactions of water-soluble MPA-CdTe QDs and NAC-CdTe QDs with mouse epidermal melanocytes B16-F10and human neuroblastoma cells SH-SY5Y were investigated by laser confocal microscopy, respectively. Preliminary results indicate that under the same conditions, the ability of MPA-CdTe QDs entering live cells was stronger than that of NAC-CdTe QDs; the ability of QDs transmembrane is dependent on cell types; and exogenous species may play a co-transport role on the intracellular distribution of QDs. In order to further improve the biocompatibility of quantum dots, the surface of the CdTe QDs was modified with the chemically reduced BSA. The results from UV spectroscopy, fluorescence spectroscopy and cell viability assay show that the denatured BSA was conjugated to the surface of CdTe QDs and made the chemical stability and biocompatibility of quantum dots be improved. In addition, we performed the preliminary comparative study on the interactions of the modified quantum dots with different stabilization agents (MPA, NAC, or dBSA) with the live cells. The results show that, at the same concentrations, the inhibition effect of CdTe QDs on the viability of live cells is in the order of MPA-> NAC-> dBSA-CdTe QDs。The experiment also showed that external factors such as UV irradiation enhanced the cytotoxicity of the quantum dots. The above study provides a theoretical clue for the synthesis of quantum dots with as higher biocompatibility and lower cytotoxicity as possible to meet the requirements of the biomedical applications.