Abstract：
Even though microplastics (MPs) and graphene nanomaterials (GNMs) have demonstrated individual toxicity towards aquatic organisms, the knowledge gap lies in the lack of understanding regarding their combined toxicity. The difference between the combined toxicity of MPs and GNMs, in contrast to their individual toxicities, and furthermore, the elucidation of the mechanism of this combined toxicity are scientific questions that remain to be addressed. In this study, we examined the individual and combined toxicity of three polystyrene microplastics (MPs) with different functional groups-unmodified, carboxyl-modified (COOH-), and amino-modified (NH2-) MPs-in combination with reduced graphene oxide (RGO) on the freshwater microalga Scenedesmus obliquus. More importantly, we explored the cellular and molecular mechanisms responsible for the observed toxicity. The results indicated that the growth inhibition toxicity of RGO, either alone or in combination with the three MPs, against S. obliquus increased gradually with higher particle concentrations. The mitigating effect of MPs-NH2 on RGO-induced toxicity was most significant at a higher concentration, surpassing the effect of unmodified MPs. However, the MPs-COOH did not exhibit a substantial impact on the toxicity of RGO. Unmodified MPs and MPs-COOH aggravated the inhibition effects of RGO on the cell membrane integrity and oxidative stress-related biomarkers. Additionally, MPs-COOH exhibited a stronger inhibition effect on RGO-induced biomarkers compared to unmodified MPs. In contrast, the MPs-NH2 alleviated the inhibition effect of RGO on the biomarkers. Furthermore, the presence of differently functionalized MPs did not significantly affect RGO-induced oxidative stress and photosynthesis-related gene expression in S. obliquus, indicating a limited ability to modulate RGO genotoxicity at the molecular level. These findings can offer a more accurate understanding of the combined risks posed by these micro- and nano-materials and assist in designing more effective mitigation strategies.
摘要：
尽管微塑料（MPs）和石墨烯纳米材料（GNMs）已经证明了对水生生物的个体毒性，知识差距在于对它们的联合毒性缺乏了解。MPs和GNMs的联合毒性之间的差异，与它们的个体毒性相反，而且,阐明这种联合毒性的机制是尚待解决的科学问题。在这项研究中,我们检查了三种具有不同官能团的聚苯乙烯微塑料（MPs）的单独和组合毒性-未改性，羧基改性（COOH-），和氨基修饰的（NH2-）MPs-与还原的氧化石墨烯（RGO）结合在淡水微藻斜生栅藻上。更重要的是,我们探索了导致观察到的毒性的细胞和分子机制。结果表明,RGO的生长抑制毒性,无论是单独还是与三名议员结合，随着颗粒浓度的升高，对斜生菌的抑制作用逐渐增加。在较高浓度下，MPs-NH2对RGO诱导的毒性的缓解作用最为显著，超越了未经修改的国会议员的影响。然而,MPs-COOH对RGO的毒性没有实质性影响。未修饰的MPs和MPs-COOH加重了RGO对细胞膜完整性和氧化应激相关生物标志物的抑制作用。此外,与未修饰的MPs相比，MPs-COOH对RGO诱导的生物标志物表现出更强的抑制作用。相比之下,MPs-NH2减轻了RGO对生物标志物的抑制作用。此外，不同功能化的MPs的存在并没有显著影响RGO诱导的氧化应激和光合作用相关基因的表达。表明在分子水平上调节RGO遗传毒性的能力有限。这些发现可以更准确地理解这些微米和纳米材料带来的综合风险，并有助于设计更有效的缓解策略。
