| Objective To prepare the folate targeting nano-TiO2compound TiO2/SiO2-NHOC-FA, and make it has good water solubility, dispersion and photocatalytic activity. It was used to photocatalytic TiO2/SiO2-NHOC-FA killing breast cancer cell line MCF-7cells under UV light irradiation, and its mechanism was explored preliminarilyMethods In order to increase the water solubility of nano-TiO2, TiO2/SiO2composite was firstly prepared by the method of hydrolysis; Secondly, TiO2/SiO2composite was modified by amino reagent and form the free amino using physical and chemical reaction; Lastly, the activated folic acid was coupled with TiO2/SiO2compound to prepare TiO2/SiO2-NHOC-FA compound using the coupling method. TiO2/SiO2-NHOC-FA was characterized by ultraviolet spectrophotometric method, Fourier infrared spectroscopy, X-ray diffraction, transmission electron microscopy and Zeta potential method. The folate receptor positive (FR+) MCF-7cells and the folate receptor negative (FR-) HepG-2were selected as the experimental subjects. The inverted phase contrast microscope was used to observe the morphology of MCF-7cells treated by photocatalytic TiO2/SiO2-NHOC-FA. The influence of different factors such as temperature, irradiation time and concentration of TiO2/SiO2-NHOC-FA on MCF-7cells was detected. The survival rate of MCF-7cells treated by photocatalytic TiO2/SiO2-NHOC-FA was detected by modified MTT method. Flow cytometry was used to detect the cell cycle and cell apoptosis rate, the change of mitochondrial membrane potential, intracellular reactive oxygen species composition and Ca2+content of MCF-7treated by photocatalytic TiO2/SiO2-NHOC-FA. The pathway of photocatalytic TiO2/SiO2-NHOC-FA killing MCF-7cells was investigated.Results Ultraviolet spectrum and infrared spectrum results showed that the TiO2/SiO2-NHOC-FA was successfully prepared. X-ray diffraction results indicated that the TiO2of TiO2/SiO2-NHOC-FA was still anatase type. Transmission electron microscopy results demonstrated that the dispersion of TiO2/SiO2-NHOC-FA was better, and the particle size was about18nm. Zeta potential results revealed that the TiO2/SiO2NHOC-FA has better stability in cell culture medium. The cytotoxicity test of TiO2/SiO2-NHOC-FA on MCF-7and HepG-2cells showed that it was less cytotoxicity, and it could be used in the photocatalytic killing MCF-7cells experiment. The experimental results of photocatalytic TiO2/SiO2-NHOC-FA killing MCF-7cells manifested that the MCF-7cells treated only with ultraviolet light was killed slightly, photocatalytic nano-TiO2and TiO2/SiO2-NHOC-FA could damage MCF-7cells significantly, and the killing effect of photocatalytic TiO2/SiO2-NHOC-FA was more stronger. The effect of photocatalytic TiO2/SiO2-NHOC-FA killing MCF-7cells on the cell cycle and the apoptosis index of MCF-7cells were investigated by flow cytometry. The results showed that photocatalytic TiO2/SiO2-NHOC-FA caused necrosis or secondary necrosis of MCF-7cells. The synthesis of DNA and their proliferation process were inhibited through arresting cell cycle of MCF-7cells in G2/M phase and inducing cell apoptosis. Yet, cell cycle of HepG-2was arrested in G0/G1phase. Photocatalytic TiO2/SiO2-NHOC-FA could significantly reduce the mitochondrial membrane potential of MCF-7cells, but increase the content of ROS components and Ca2+. These changes of apoptosis index indicated that photocatalytic TiO2/SiO2-NHOC-FA could induce cell apoptosis. The MCF-7cells died in forms of cell apoptosis and necrosis, and the cell apoptosis was main.Conclusion The water solublility and dispersion of TiO2/SiO2-NHOC-FA prepared in this experiment was better than that of nano-TiO2, and the efficiency of photocatalytic TiO2/SiO2-NH OC-FA killing MCF-7cells was also improved greatly. The highest killing efficiency52%was achieved by photocatalytic TiO2/SiO2-NHOC-FA killing MCF-7cells, when the irradiation time was30min, temperature was37℃, and TiO2/SiO2-NHOC-FA concentration was200μg·ml-1Photocatalytic TiO2/SiO2-NHOC-FA mainly killed MCF-7cells by apoptosis pathway. |
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