| In this paper, we use combined methods such as SEM, ICP—AES, fluorescence polarization, QDs labeling fluorescence microscope to study the cell (procaryotic cell and eukaryotic cell) damage after different treatment. In addition, we synthesize TiO2/MWCNTs nanocompositesto enhance the photocatalytic efficiency and study the antibiotic effect by using E.coli. The main results and conclusions are summarized as follows:1, For Tetrahymena cells treated by TiO2 or UV light alone, membrane shrunk to some extent. But the cells could still keep the original elliptoid shape. The cells treated by TiO2 under UV light irradiation experienced the most serious damage of peroxidation. The pear shape was formed due to the serious shrinkage and the cilia lost a lot. The fluorescence polarization reflected a significant decrease in membrane fluidity. Another experiment was designed to prove the permeability changes by QDs labelling. The results revealed that the damaged cells could not absorb the extracellular materials selectively. QDs could enter the cells or be absorbed on the cell surface. ATR—FTIR spectra revealed that amide groups and PO2- of the phospho-lipid phospho-diester, both in the hydrophobic end exposed to the outer layer, were the easiest to be oxidized, other groups like-CH2,-CH3 also were involved, but at a slower pace, showing a higher resistance to photocatalytic peroxidation.2, For E.coli cells treated by TiO2 or UV light alone, LPS rupture to some extent. But the cells could still keep the original rod shape. The cells treated by TiO2 under UV light irradiation experienced the most serious damage of outer membrane, and the spheroplasts were formed. The outer cell membrane was almost completely removed because cells can no longer maintain the cell morphology. The release of Ca2+, Mg2+ on LPS patches comfirmed the results of SEM observation. With more LPS patches rupturing, more Ca2+, Mg2+ were released to the medium. The decreasing fluidity observed by fluorescent polarization, and the membrane permeability increased. To summarize, E.coli under intense UV light was damaged by the high-energy proton. E.coli treated with TiO2 under UV light showed the highest photocatalytic damage because much more free radicals were produced under UV light. Tthe cells that became elliptical or round indicated the outer membrane including LPS, peptidoglycan and a phospholipid layer was destroyed, whlile the inner membrane still existed, and otherwise the cell would break apart and can not be seen.3, we sythzised TiO2/MWCNTs nanocomposites and it showed the best photocatalystic effect when TiO2/MWCNTs mass ratio was 1:10 and its degradation efficiency of methylene blue(MB) was about 50% higher than pure TiO2. As to the different radii of MWCNTs, the smaller the radius was, the mote contact points there wre between MWCNTs and TiO2, and the higher contents of MWCNTs in this nanocomposites. This would benefit the conduction of electrons, lowered the probability of electron-hole recombination, and thus enhance the pgotocatalytis efficiency. TG-DSC results revealed that at 70℃free water on the surface started dehydrated and the hydroxyl groups lost between 300℃to 400℃, accompanied by some organic compounds decomposition. From the SEM photos, we would see that E.coli after photocatalysis by TiO2/MWCNTs nanocomposites became elliptical or round. ATR-FTIR spectrum showed tha hydroxyl groups on t the outmost LPS were the easiest to be oxidized, followed by amide groups and PO2- of the phospho-lipid phospho-diester both in the hydrophobic end. Other groups like CH2, CH3 also were involved, but at a slower pace, showing a higher resistance to photocatalytic peroxidation. The shifts of C-H band position in ATR-FTIR spectrum suggested the alteration of the fatty tail structure due to increased structural disorder leading to increased fluidity, permeability and the malfunction of membrane selective absorption...
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