Iswarya V, Sharma Vineet, Chandrasekaran N, Mukherjee Amitava
Centre for Nanobiotechnology, VIT University, Vellore, 632014, India.
Centre for Nanobiotechnology, VIT University, Vellore, 632014, India.
Aquat Toxicol. 2017 Dec;193:168-177. doi: 10.1016/j.aquatox.2017.10.023. Epub 2017 Oct 26.
Titanium dioxide nanoparticles (TiO NPs) are the most risk assessed nanoparticles in the aquatic environment due to their increased usage in the various sectors from electronics to consumer products. The natural aquatic system also comprises of numerous toxicants like antibiotics, whose impact on the toxicity of nanoparticles are less assessed. Hence, it is essential to determine the effect of other toxicants on the TiO NP toxicity. In the current study, the impact of antibiotic (tetracycline, TC) on the toxic effect of TiO NPs was studied on a freshwater alga, Scenedesmus obliquus. The median effective concentrations (EC) of TiO NPs and TC were noted to be 136.88±2.30μM and 0.63±0.02μM, respectively. Based on the EC obtained, three different concentrations of TC, such as 0.34, 0.68, and 1.36μM have been selected to evaluate their effect on the toxicity of 18.75, 37.5, and 75μM of TiO NPs. Existence of TC provoked the growth inhibition of TiO NPs at their lower concentrations. In contrast, a reduction in the growth inhibition was noted as the concentrations of TC and TiO NPs were increased. Abbott modeling confirmed the additive and antagonistic effects noted. The stability profile of TiO NPs elucidated the aggregation of NPs with an increase in time. Even though a similar trend has been followed for TiO NPs+TC, a significant difference in the aggregation has not been observed in most cases when compared with TiO NPs alone. The presence of TC lowered the Ti uptake by the algal cells, which portrayed the dominance of TC in the toxic effect of TiO NPs to be either additive or antagonistic. The SEM images of the algal cells upon exposure to TiO NPs, TC, and their mixture elucidated the aggregation of algal cells, cellular deformations like compromised cell membrane, and vacuole formation, etc. In addition, the release of algal exudates was also noticed as a protective layer over the cells to counteract the stress. EPS secretion in response to TiO NPs along with TC is found to be in corroboration with the toxicity patterns observed.
二氧化钛纳米颗粒（TiO NPs）是水环境中风险评估最多的纳米颗粒，因为它们在从电子到消费品的各个领域中的使用量都在增加。天然水生系统中还包含许多有毒物质，如抗生素，而抗生素对纳米颗粒毒性的影响评估较少。因此，确定其他有毒物质对TiO NP毒性的影响至关重要。在当前的研究中，研究了抗生素（四环素，TC）对淡水绿藻斜生栅藻中TiO NPs毒性作用的影响。TiO NPs和TC的半数有效浓度（EC）分别为136.88±2.30μM和0.63±0.02μM。根据获得的EC，选择了三种不同浓度的TC，即0.34、0.68和1.36μM，以评估它们对18.75、37.5和75μM的TiO NPs毒性的影响。TC的存在在较低浓度下引发了TiO NPs的生长抑制。相反，随着TC和TiO NPs浓度的增加，生长抑制作用降低。Abbott模型证实了所观察到的相加和拮抗作用。TiO NPs的稳定性曲线表明，随着时间的增加，纳米颗粒会发生聚集。尽管TiO NPs+TC也呈现出类似的趋势，但与单独的TiO NPs相比，在大多数情况下未观察到聚集有显著差异。TC的存在降低了藻类细胞对钛的吸收，这表明在TiO NPs的毒性作用中，TC的主导作用为相加或拮抗。暴露于TiO NPs、TC及其混合物后，藻类细胞的扫描电子显微镜图像显示了藻类细胞的聚集、细胞膜受损等细胞变形以及液泡形成等情况。此外，还注意到藻类分泌物的释放，作为细胞上的保护层以应对压力。发现响应TiO NPs和TC的胞外聚合物分泌与观察到的毒性模式一致。
