title: Uptake and effect of highly fluorescent silver nanoclusters on Scenedesmus obliquus.
abstract: The release of silver nanoparticles (Ag NPs) in aquatic environment has caused wide public concern about their effects on living organisms (e.g., algae). However, how these small NPs exert cytotoxicity in the living organisms has always been under heated debate. In this study, the uptake and toxicity effects of strongly red-emitting fluorescent silver nanoclusters (r-Ag NCs) exposed to the green algae Scenedesmus obliquus was investigated. Upon exposure to pure r-Ag NCs and r-Ag NCs containing l-cysteine, the algae growth inhibition test showed that Ag(+) ions released from r-Ag NCs played an important role in the toxicity of r-Ag NCs along with the toxicity of intact r-Ag NCs. Furthermore, no signals of intracellular reactive oxygen species (ROS) were observed indicating that r-Ag NCs or released Ag(+) ions - mediated growth inhibition of algae cells was independent of ROS production. Transmission electron microscopy (TEM) and laser scanning confocal microscopy (LSCM) were employed to study cellular uptake and cytotoxicity. Furthermore, analysis of differential expressed gene demonstrated that r-Ag NCs as well as the released Ag(+) ions can simultaneously exist inside the algae cells, and inhibit the transcriptomic process of genes by their "joint-toxicity" mechanism. Taken together, our study provides a new insight into the molecular mechanisms of r-Ag NCs and Ag(+) ions exposure to the aquatic organism and can be applied to early diagnosis of ecologic risk mediated by others metal-based NPs.
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiao Tong University, No. 800 Dongchuan Road, Minhang District, Shanghai, 200240, China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiao Tong University, No. 800 Dongchuan Road, Minhang District, Shanghai, 200240, China. Electronic address: ylhe@sjtu.edu.cn.
authors.forename: Yiliang
authors.initials: Y
authors.lastname: He
authors.affiliation: Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, #03-18, 117585, Singapore.
authors.forename: Nirmal
authors.initials: N
authors.lastname: Goswami
authors.affiliation: Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, #03-18, 117585, Singapore.
authors.forename: Jianping
authors.initials: J
authors.lastname: Xie
authors.affiliation: School of Environmental Science and Engineering, Shanghai Jiao Tong University, No. 800 Dongchuan Road, Minhang District, Shanghai, 200240, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.affiliation: College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, 201306, China.
authors.forename: Xianji
authors.initials: X
authors.lastname: Tao
mesh_terms: D001692:Biological Transport; D003545:Cysteine / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000378:metabolism*; D053768:Metal Nanoparticles / Q000633:toxicity*; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D017382:Reactive Oxygen Species / Q000378:metabolism; D044444:Scenedesmus / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D012834:Silver / Q000378:metabolism* / Q000633:toxicity*
chemical_list: D005456:Fluorescent Dyes; D017382:Reactive Oxygen Species; D012834:Silver; D003545:Cysteine
keywords: Fluorescence; Joint-toxicity; Scenedesmus obliquus; Silver nanoclusters; Transcriptomic analysis