Joost Urmas, Juganson Katre, Visnapuu Meeri, Mortimer Monika, Kahru Anne, Nõmmiste Ergo, Joost Urmeli, Kisand Vambola, Ivask Angela
Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu, Estonia; Estonian Nanotechnology Competence Center, Ravila 14c, 50411 Tartu, Estonia.
Laboratory of Environmental Toxicology, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia; Department of Chemistry, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia.
J Photochem Photobiol B. 2015 Jan;142:178-85. doi: 10.1016/j.jphotobiol.2014.12.010. Epub 2014 Dec 17.
Titanium dioxide is a photocatalyst with well-known ability to oxidise a wide range of organic contaminants as well as to destroy microbial cells. In the present work TiO2 nanoparticles with high specific surface area (150m(2)/g) were used to prepare nanostructured films. The TiO2 nanoparticle-based film in combination with UV-A illumination with intensity (22W/m(2)) comparable to that of the sunlight in the UV-A region was used to demonstrate light-induced antibacterial effects. Fast and effective inactivation of Escherichia coli cells on the prepared thin films was observed. Visualization of bacterial cells under scanning electron microscopy (SEM) showed enlargement of the cells, distortion of cellular membrane and possible leakage of cytoplasm after 10min of exposure to photoactivated TiO2. According to the plate counts there were no viable cells as early as after 20min of exposure to UV-A activated TiO2. In parallel to effects on bacterial cell viability and morphology, changes in saturated and unsaturated fatty acids - important components of bacterial cell membrane-were studied. Fast decomposition of saturated fatty acids and changes in chemical structure of unsaturated fatty acids were detected. Thus, we suggest that peroxidation and decomposition of membrane fatty acids could be one of the factors contributing to the morphological changes of bacteria observed under SEM, and ultimately, cell death.
二氧化钛是一种光催化剂，具有氧化多种有机污染物以及破坏微生物细胞的知名能力。在本研究中，使用具有高比表面积（150m²/g）的TiO₂纳米颗粒制备纳米结构薄膜。将基于TiO₂纳米颗粒的薄膜与强度（22W/m²）与UV-A区域的阳光相当的UV-A光照相结合，用于证明光诱导的抗菌效果。观察到制备的薄膜上大肠杆菌细胞快速且有效地失活。扫描电子显微镜（SEM）下细菌细胞的可视化显示，在暴露于光活化的TiO₂ 10分钟后，细胞增大、细胞膜变形以及可能的细胞质泄漏。根据平板计数，早在暴露于UV-A活化的TiO₂ 20分钟后就没有活细胞了。与对细菌细胞活力和形态的影响并行，研究了饱和脂肪酸和不饱和脂肪酸（细菌细胞膜的重要组成部分）的变化。检测到饱和脂肪酸的快速分解和不饱和脂肪酸化学结构的变化。因此，我们认为膜脂肪酸的过氧化和分解可能是导致在SEM下观察到的细菌形态变化并最终导致细胞死亡的因素之一。
