γ-radiation Synthesis Of Water-soluble Quantum Dots And Their Bioeffects In Cells

Quantum dots (QDs), as an important member of nanomaterials, have been gaining popularity due to their unique electrical and optical properties. QDs have wide potential applications in optoelectronics and biomedical areas. Besides the excellent optical properties, QDs should have good water-solubility, excellent biocompatibility and low cytotoxicity before they can be applied in biomedical area. Focusing on the key issues involved in the biomedical application of QDs, we mainly carried out the synthesis of water-soluble QDs and the study of their bioeffects in this thesis. First, the natural polymer (silk fibroin and chitosan) modified water-soluble QDs were successfully synthesized via a one-stepγ-radiation route in an aqueous at room temperature. A new synthesis strategy was explored to fabricate quasi-zero-dimensional nanomaterials underγ-irradiation based on natural polymer stabilizer. Then, the cellular distribution, metabolism and cytotoxicity of QDs in PANC-1 cells were studied. The cytotoxicity of MPA-CdTe QDs under UV irradiation was also investigated. The gained research results were as follows:1)The functional silk fibers modified by Ag nanoparticles and CdS QDs were successfully fabricated viaγ-ray irradiation. The microstructure and properties were characterized and all results revealed that the products had excellent antimicrobial capability or luminescence properties.The optimum reaction conditions and mechanism were discussed, which would provide a good idea to prepare SF and CS modified QDs in next section.2) Silk fibroin (SF) coated CdSe and ZnSe:Mn²⁺ QDs were successfully synthesized via a one-stepγ-radiation route in an aqueous system. The microstructure, photoluminescence, magnetic properties, cellular metabolism and cytotoxicity of products were characterized. The optimum reaction conditions and mechanism were also discussed. SF-CdSe QDs exhibited excellent water-solubility and photoluminescence properties. SF-CdSe QDs could be easily internalized by cells and proved to be low cytotoxicity and high photostability. SF-ZnSe:Mn²⁺ QDs also had good water-solubility and photoluminescence properties and exhibited excellent superparamagnetic behavior when the temperature was above 10 K.3) Water-soluble chitosans (CS) with low molecular weight were successfully prepared by theγ- radiation depolymerization method. The influences of irradiation dose and preprocessing methods on molecular weight, chemical structure and Gd were detailedly discussed and the optimum reaction conditions were explored.4) Chitosan modified CdSe, ZnS and ZnS:Mn²⁺ QDs were successfully synthesized via a one-stepγ-radiation route in an aqueous system. The microstructure and photoluminescence properties were characterized and the results revealed that the products exhibited excellent water-solubility and photoluminescence properties. The influences of reaction conditions on the products were detailedly discussed and the optimum reaction conditions were explored. The reaction mechanism was also proposed.5) A new synthesis strategy was developed to fabricate quasi-zero-dimensional nanomaterials underγ-irradiation based on natural polymer stabilizer. Silk fibroin and chitosan were natural polymers, so the QDs modified by them were proved to be excellent biocompatibility and have many potential applications. This synthesis strategy was very simple and could be conveniently extended to fabricate other nanoparticles modified by SF or CS.6) MPA-CdTe QDs(QD₅38,QD₅61,QD₅80,QD₆05å’ŒQD₆29)and Cys-CdTe QDs(QD₅43)were successfully prepared and proved to have good water-solubility and photoluminescence properties. Using above different CdTe QDs, we studied the influences of particle size, QDs concentration in medium, surface modification state, incubation time with QDs and incubation time after QDs treatment on the cellular distribution, metabolism and cytotoxicity of QDs. The relevant mechanism was also generally discussed.7) The results revealed that green and red MPA-CdTe QDs dissolved in water or PBS exhibited excellent photostability under UV irradiation. The morphological changes and viability decrease of PANC-1 cells induced by green and red MPA-CdTe QDs under UV irradiation were detailedly studied. The influences of UV irradiation time, concentration of QDs, incubation time with QDs and incubation time after UV irradiation on the UV enhanced cytotoxicity of QDs were also investigated.8) The generation of ROS in PANC-1 cells containing QDs under UV irradiation was investigated. The results revealed that UV irradiation could enhance the generation of ROS in cells, and NAC antioxidant could reduce the generation of ROS and reduce the damages of cells under UV irradiation. Moreover, the process and mechanism of UV enhanced cytotoxicity of QDs were generally discussed.