School of Ecology and Environment, Anhui Normal University, Wuhu 241002, China; Collaborative Innovation Center of Recovery and Reconstruction of Degraded Ecosystem in Wanjiang Basin Co-founded by Anhui Province and Ministry of Education, Wuhu 241002, China.
College of Chemistry & Pharmacy, Northwest A & F University, Yangling 712100, Shaanxi, China.
Ecotoxicol Environ Saf. 2023 Feb;251:114556. doi: 10.1016/j.ecoenv.2023.114556. Epub 2023 Jan 18.
Nano titanium dioxide (nTiO) generally shows low toxicity to organisms under light-emitting diode (LED) light. However, nTiO can induce production of reactive oxygen species (ROS) under ultraviolet (UV) light due to its photocatalytic activity. Therefore, it is reasonable to expect the enhancement of nTiO toxicity under sunlight. To test this hypothesis, we compared the toxicity of nTiO to Brachionus calyciflorus under simulated sunlight and LED light. The results showed that the 24 h-LC of nTiO to B. calyciflorus under LED light and simulated sunlight were 24.32 (95% CI: 14.54-46.81 mg/L) and 10.44 mg/L (95% CI: 6.74-17.09 mg/L), respectively. Compared with the blank control, treatments with nTiO significantly affected life-table demographic parameters, population growth parameters and swimming linear speed under both simulated sunlight and LED light. However, life expectancy, net reproductive rate, average lifespan, maximal population density, and swimming linear speed in the treatments of nTiO at 0.1, 1, and/or 10 mg/L showed markedly lower values under simulated sunlight than those under LED light, suggesting that simulated sunlight could enhance the toxicity of nTiO. In addition, markedly higher catalase (CAT) activity and malondialdehyde (MDA) content but lower glutathione (GSH) content were observed in treatment with 10 mg/L nTiO under simulated sunlight than that under LED light. The results showed that compared with LED light, simulated sunlight significantly induced more oxidative stress in the presence of nTiO, and the ROS production was mainly localized to the corona and digestive tract of rotifers by confocal laser scanning microscope. Exposure to 10-50 μM of vitamin C, that is an effective ROS scavenger, could rescue the swimming linear speed of rotifers to the normal level in the blank control. These results suggested that oxidative damages on cell membrane might be the vital mechanism underlying the toxicity enhancement of nTiO to rotifers under simulated sunlight. Thus, the previous publications under LED light may underestimate the real toxicity and environmental risk of nTiO in natural conditions.
纳米二氧化钛（nTiO）在发光二极管（LED）光下通常对生物体显示出低毒性。然而，由于其光催化活性，nTiO 在紫外（UV）光下可以诱导活性氧物种（ROS）的产生。因此，有理由期望在阳光照射下增强 nTiO 的毒性。为了验证这一假设，我们比较了 nTiO 对花束钟形臂尾轮虫的毒性在模拟阳光和 LED 光下。结果表明，nTiO 在 LED 光和模拟阳光下对 B. calyciflorus 的 24 小时 LC 分别为 24.32（95%CI：14.54-46.81mg/L）和 10.44mg/L（95%CI：6.74-17.09mg/L）。与空白对照相比，在模拟阳光和 LED 光下，nTiO 的处理均显著影响生命表人口参数、种群增长参数和游泳线性速度。然而，在 0.1、1 和/或 10mg/L 的 nTiO 处理下，预期寿命、净生殖率、平均寿命、最大种群密度和游泳线性速度在模拟阳光下的值明显低于 LED 光下的值，表明模拟阳光可以增强 nTiO 的毒性。此外，在模拟阳光下，10mg/L nTiO 处理的过氧化氢酶（CAT）活性和丙二醛（MDA）含量明显高于 LED 光下的值，谷胱甘肽（GSH）含量明显低于 LED 光下的值。结果表明，与 LED 光相比，模拟阳光在存在 nTiO 的情况下显著诱导了更多的氧化应激，并且通过共聚焦激光扫描显微镜，ROS 的产生主要定位于轮虫的冠和消化道。暴露于 10-50μM 的维生素 C，即一种有效的 ROS 清除剂，可以将轮虫的游泳线性速度恢复到空白对照的正常水平。这些结果表明，细胞膜的氧化损伤可能是 nTiO 在模拟阳光下对轮虫毒性增强的重要机制。因此，以前在 LED 光下发表的论文可能低估了 nTiO 在自然条件下的真实毒性和环境风险。
