Abstract The extensive application of titanium dioxide nanoparticles (TiO2 NPs) has raised concern about its environmental risks. The present study aims to elucidate TiO2 NP ecotoxicity, by assessing effects on seagrasses at environmentally relevant concentrations. Changes in physiological and structural cell traits of Cymodocea nodosa leaves, treated with TiO2 NPs at 0.0015–1.5 mg l−1 for eight consecutive days, were investigated. Intracellular levels of hydrogen peroxide (H2O2) increased significantly, even early during the lowest exposure, despite an up-regulation of H2O2-scavenging enzyme activity. Actin filaments (AFs) and endoplasmic reticulum (ER) were affected in a concentration- and time-dependent pattern, while no changes in microtubule organization and cell ultrastructure were detected. The lowest effect concentrations for AF and ER impairment were 0.15 and 1.5 mg l−1, respectively; for cell death, these were 0.15–1.5 mg l−1, depending on leaf age, and for leaf elongation inhibition 0.15 mg l−1. Thus, elevated H2O2 level can be considered as an early warning biomarker for TiO2 NPs, while leaf elongation, AF and ER impairment are also reliable indicators. A risk quotient greater than 1 was estimated; thus, TiO2 NPs might present a significant potential environmental risk. Our findings can be utilized for monitoring pollution levels in coastal environments.

中文翻译：

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海草 Cymodocea nodosa 对二氧化钛纳米颗粒暴露的生理和结构响应

摘要 二氧化钛纳米粒子（TiO2 NPs）的广泛应用引起了人们对其环境风险的关注。本研究旨在通过评估环境相关浓度对海草的影响来阐明 TiO2 NP 的生态毒性。研究了连续 8 天用 0.0015–1.5 mg l-1 的 TiO2 NPs 处理的 Cymodocea nodosa 叶子的生理和结构细胞特征的变化。尽管 H2O2 清除酶活性上调，但细胞内过氧化氢 (H2O2) 的水平显着增加，即使在最低暴露期间也是如此。肌动蛋白丝 (AFs) 和内质网 (ER) 受到浓度和时间依赖性模式的影响，而未检测到微管组织和细胞超微结构的变化。AF 和 ER 损伤的最低效应浓度分别为 0.15 和 1.5 mg l-1；对于细胞死亡，这些是 0.15–1.5 mg l-1，取决于叶龄，而对于叶片伸长抑制，则为 0.15 mg l-1。因此，升高的 H2O2 水平可被视为 TiO2 NPs 的预警生物标志物，而叶片伸长、AF 和 ER 损伤也是可靠的指标。估计的风险商数大于 1；因此，TiO2 NPs 可能存在显着的潜在环境风险。我们的发现可用于监测沿海环境的污染水平。AF 和 ER 减值也是可靠的指标。估计的风险商数大于 1；因此，TiO2 NPs 可能存在显着的潜在环境风险。我们的发现可用于监测沿海环境的污染水平。AF 和 ER 减值也是可靠的指标。估计的风险商数大于 1；因此，TiO2 NPs 可能存在显着的潜在环境风险。我们的发现可用于监测沿海环境的污染水平。