Extracellular polymeric substances altered the physicochemical properties of molybdenum disulfide nanomaterials to mitigate its toxicity to Chlorella vulgaris

Manman Cao; Donghong Yang; Fei Wang; Beihai Zhou; Huilun Chen; Rongfang Yuan; Ke Sun

doi:10.1016/j.impact.2023.100485

Extracellular polymeric substances altered the physicochemical properties of molybdenum disulfide nanomaterials to mitigate its toxicity to Chlorella vulgaris

NanoImpact. 2023 Oct:32:100485. doi: 10.1016/j.impact.2023.100485. Epub 2023 Sep 29.

Authors

Manman Cao¹, Donghong Yang², Fei Wang³, Beihai Zhou², Huilun Chen², Rongfang Yuan², Ke Sun¹

Affiliations

¹ School of Environment, Beijing Normal University, 19 Xinjiekouwai Street, 100875 Beijing, China.
² School of Energy & Environmental Engineering, Beijing Key Laboratory of Resource-Oriented Treatment of Industrial Pollutants, University of Science and Technology Beijing, 30 Xueyuan Road, 100083 Beijing, China.
³ School of Environment, Beijing Normal University, 19 Xinjiekouwai Street, 100875 Beijing, China. Electronic address: feiwang@bnu.edu.cn.

PMID: 37778438
DOI: 10.1016/j.impact.2023.100485

Abstract

Although the toxic effects of two-dimensional nanomaterials (2D-NMs) have been widely reported, the influence of extracellular polymeric substances (EPS) on the environmental fate and risk of 2D-NMs in aquatic environments is largely unknown, and the processes and mechanisms involved remain to be revealed. Herein, we investigated the impact of EPS secreted by microalgae (Chlorella vulgaris (C. vulgaris)) on the environmental transformation and risk of molybdenum disulfide (MoS₂). We found that the attachment of EPS increased the thickness of MoS₂ (from 2 nm to 5 nm), changed it from a monolayer sheet to a fuzzy multilayer structure, and promoted the formation of defects on MoS₂. The blue-shift of the peak associated with the plasmon resonances in the 1 T phase and the generation of electron-hole pairs suggested that EPS altered the surface electronic structure of MoS₂. EPS interacted mainly with the S atoms on the 1 T phase, and the attachment of EPS promoted the oxidation of MoS₂. The reduction in hydrodynamic diameter (D_h) and the decrease in zeta potential indicated that EPS inhibited the agglomeration behavior of MoS₂ and enhanced its dispersion and stability in aqueous media. Notably, EPS reduced the generation of free radicals (superoxide anion (•O₂^-), singlet oxygen (¹O₂), and hydroxyl radicals (•OH^-)). Furthermore, EPS mitigated the toxicity of MoS₂ to C. vulgaris, such as attenuated reduction in biomass and chlorophyll content. Compared to pristine MoS₂, MoS₂ + BG11 + EPS exhibited weaker oxidative stress, membrane damage and lipid peroxidation. The adsorption of EPS on MoS₂ surface reduced the attachment sites of MoS₂, making MoS₂ less likely to be enriched on the cell surface. The findings have significant contribution for understanding the interactions between EPS and MoS₂ in aquatic ecosystems, providing scientific guidance for risk assessment of 2D-NMs.

Keywords: Aquatic environment; Environmental risk; Extracellular polymeric substances; Freshwater algae; Molybdenum disulfide.

MeSH terms

Chlorella vulgaris*
Ecosystem
Extracellular Polymeric Substance Matrix / chemistry
Molybdenum / toxicity
Nanostructures* / toxicity

Substances

molybdenum disulfide
Molybdenum