title: Sulfidation as a natural antidote to metallic nanoparticles is overestimated: CuO sulfidation yields CuS nanoparticles with increased toxicity in medaka (Oryzias latipes) embryos.
abstract: Sulfidation is considered as a natural antidote to toxicity of metallic nanoparticles (NPs). The detoxification contribution from sulfidation, however, may vary depending on sulfidation mechanisms. Here we present the dissolution-precipitation instead of direct solid-state-shell mechanism to illustrate the process of CuO-NPs conversion to CuS-NPs in aqueous solutions. Accordingly, the CuS-NPs at environmentally relevant concentrations showed much stronger interference on Japanese medaka (Oryzias latipes) embryo hatching than CuO-NPs, which was probably due to elevated free copper ions released from CuS-NPs, leading to significant increase in oxidative stress and causing toxicity in embryos. The larval length was significantly reduced by CuS-NPs, however, no other obviously abnormal morphological features were identified in the hatched larvae. Co-introduction of a metal ion chelator [ethylene diamine tetraacetic acid (EDTA)] could abolish the hatching inhibition induced by CuS-NPs, indicating free copper ions released from CuS-NPs play an important role in hatching interference. This work documents for the first time that sulfidation as a natural antidote to metallic NPs is being overestimated, which has far reaching implications for risk assessment of metallic NPs in aquatic environment.
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , No. 18, Shuangqing Road, Haidian, Beijing 100085, China.
authors.forename: Lingxiangyu
authors.initials: L
authors.lastname: Li
authors.forename: Ligang
authors.initials: L
authors.lastname: Hu
authors.forename: Qunfang
authors.initials: Q
authors.lastname: Zhou
authors.forename: Chunhua
authors.initials: C
authors.lastname: Huang
authors.forename: Yawei
authors.initials: Y
authors.lastname: Wang
authors.forename: Cheng
authors.initials: C
authors.lastname: Sun
authors.forename: Guibin
authors.initials: G
authors.lastname: Jiang
mesh_terms: D000818:Animals; D000931:Antidotes; D003300:Copper / Q000737:chemistry* / Q000633:toxicity*; D053768:Metal Nanoparticles / Q000633:toxicity*; D009990:Oryzias / Q000196:embryology*; D018384:Oxidative Stress; D013440:Sulfides / Q000737:chemistry*
chemical_list: D000931:Antidotes; D013440:Sulfides; D003300:Copper; C017846:cupric sulfide; C030973:cupric oxide