Metal oxide nanoparticles (NPs) are increasingly used in many industrial and biomedical applications, hence their impact on occupational and public health has become a concern. In recent years, interest on the effect that exposure to NPs may exert on human reproduction has grown, however data are still scant. In the present work, we investigated whether different metal oxide NPs interfere with mouse cumulus cell-oocyte complex (COC) expansion. Mouse COCs from pre-ovulatory follicles were cultured in vitro in the presence of various concentrations of two types of TiO2 NPs (JRC NM-103 and NM-104) and four types of ZnO NPs (JRC NM-110, NM-111, and in-house prepared uncoated and SiO2-coated NPs) and the organization of a muco-elastic extracellular matrix by cumulus cells during the process named cumulus expansion was investigated. We show that COC expansion was not affected by the presence of both types of TiO2 NPs at all tested doses, while ZnO NM-110 and NM-111 induced strong toxicity and inhibited COCs expansion at relatively low concentration. Medium conditioned by these NPs showed lower toxicity, suggesting that, beside ion release, inhibition of COC expansion also depends on NPs per se. To further elucidate this, we compared COC expansion in the presence of uncoated or SiO2-coated NPs. Differently from the uncoated NPs, SiO2-coated NPs underwent slower dissolution, were not internalized by the cells, and showed an overall lower toxicity. Gene expression analysis demonstrated that ZnO NPs, but not SiO2-coated ZnO NPs, affected the expression of genes fundamental for COC expansion. Dosimetry analysis revealed that the delivered-to-cell mass fractions for both NPs was very low. Altogether, these results suggest that chemical composition, dissolution, and cell internalization are all responsible for the adverse effects of the tested NPs and support the importance of a tailored, safer-by-design production of NPs to reduce toxicity.

中文翻译：

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氧化锌纳米颗粒的二氧化硅包封降低了它们对卵丘细胞-卵母细胞-复合物扩增的毒性

金属氧化物纳米粒子 (NPs) 越来越多地用于许多工业和生物医学应用，因此它们对职业和公共健康的影响已成为一个问题。近年来，人们对暴露于 NPs 可能对人类生殖产生影响的兴趣越来越大，但数据仍然很少。在目前的工作中，我们研究了不同的金属氧化物纳米颗粒是否会干扰小鼠卵丘细胞 - 卵母细胞复合物 (COC) 的扩增。来自排卵前卵泡的小鼠 COC 在不同浓度的两种 TiO2 NP（JRC NM-103 和 NM-104）和四种 ZnO NP（JRC NM-110、NM-111 和内部制备的未包被和 SiO2 包被的 NPs) 以及在称为积云扩展的过程中由积云细胞组织粘液弹性细胞外基质。我们表明，在所有测试剂量下，两种类型的 TiO2 NPs 的存在都不会影响 COC 的膨胀，而 ZnO NM-110 和 NM-111 会诱导强烈的毒性并在相对较低的浓度下抑制 COCs 的膨胀。由这些 NPs 调节的培养基显示出较低的毒性，这表明除了离子释放之外，对 COC 膨胀的抑制也取决于 NPs 本身。为了进一步阐明这一点，我们比较了在未涂覆或 SiO2 涂覆的 NPs 存在下的 COC 膨胀。与未包被的 NPs 不同，SiO2 包被的 NPs 溶解速度较慢，不被细胞内化，总体毒性较低。基因表达分析表明 ZnO NPs，而不是 SiO2 包覆的 ZnO NPs，影响 COC 扩展的基础基因的表达。剂量学分析表明，两种纳米颗粒的递送至细胞质量分数都非常低。总而言之，这些结果表明化学成分、溶解和细胞内化都对测试的 NPs 的不利影响负责，并支持量身定制、按设计更安全地生产 NPs 以降低毒性的重要性。