Carbon nanodots (CNDs) have been studied in the field of biomedicine, such as drug delivery, bioimaging and theragnosis because of their superior biocompatibility and desirable optoelectronic properties. However, limited assessments on the biological effects of CNDs, particularly the effect on oxidative stress and toxicity in living cells, are not adequately addressed. In this work, a type of nitrogen, sulfur-doped carbon nanodots (N,S-CNDs), which were found to have strong antioxidant capacity in free radical scavenging in physicochemical conditions, was investigated through measuring the fluctuations of the intracellular reactive oxygen species (ROS), such as the hydrogen peroxide and superoxide anion, at different dose exposure in two types of cell lines, EA.hy926 and A549 cells. Instead of showing antioxidative capacity, the results indicate the uptake of the N,S-CNDs induces the production of intracellular ROS, thus causing oxidative stress and deleteriousness to both cell lines. The mitochondrial membrane potential of the cells was monitored upon the N,S-CNDs treatment and found to increase monotonically with the concentration of the CNDs. In addition, the confocal imaging of the cells confirms the localization of the CNDs at the mitochondria. More evidence suggests that the N,S-CNDs may stimulate ROS generation by interacting with the electron transport chain in the mitochondrial membrane due to the sulfur composite in the CNDs.

中文翻译：

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活体 EA.hy926 和 A549 细胞中氮和硫共掺杂的碳纳米点：氧化应激效应和线粒体靶向

碳纳米点 (CND) 因其优异的生物相容性和理想的光电特性而在生物医学领域进行了研究，例如药物递送、生物成像和治疗。然而，对 CND 的生物学效应的有限评估，特别是对活细胞中氧化应激和毒性的影响，没有得到充分的解决。在这项工作中，通过测量细胞内活性氧的波动，研究了一种在物理化学条件下具有很强的自由基清除能力的氮、硫掺杂碳纳米点（N,S-CNDs）。 (ROS)，例如过氧化氢和超氧阴离子，在两种类型的细胞系 EA.hy926 和 A549 细胞中以不同的剂量暴露。而不是表现出抗氧化能力，结果表明，N,S-CNDs 的摄取会诱导细胞内 ROS 的产生，从而对两种细胞系造成氧化应激和有害作用。在 N,S-CNDs 处理后监测细胞的线粒体膜电位，发现随着 CNDs 的浓度单调增加。此外，细胞的共聚焦成像证实了 CND 在线粒体中的定位。更多证据表明，由于 CND 中的硫复合物，N,S-CND 可能通过与线粒体膜中的电子传递链相互作用来刺激 ROS 的产生。S-CNDs 处理并发现随着 CNDs 的浓度单调增加。此外，细胞的共聚焦成像证实了 CND 在线粒体中的定位。更多证据表明，由于 CND 中的硫复合物，N,S-CND 可能通过与线粒体膜中的电子传递链相互作用来刺激 ROS 的产生。S-CNDs 处理并发现随着 CNDs 的浓度单调增加。此外，细胞的共聚焦成像证实了 CND 在线粒体中的定位。更多证据表明，由于 CND 中的硫复合物，N,S-CND 可能通过与线粒体膜中的电子传递链相互作用来刺激 ROS 的产生。