Abstract
The unique properties of engineered nanoparticles (ENs) that make their industrial applications so attractive simultaneously raise questions regarding their environmental safety. ENs exhibit behaviors different from bulk materials with identical chemical compositions. Though the nanotoxicity of ENs has been studied intensively, their unintended environmental impacts remain largely unknown. Herein we report experimental results of EN interactions with exopolymeric substances (EPS) from three marine phytoplankton species: Amphora sp., Ankistrodesmus angustus and Phaeodactylum tricornutum. EPS are polysaccharide-rich anionic colloid polymers released by various microorganisms that can assemble into microgels, possibly by means of hydrophobic and ionic mechanisms. Polystyrene nanoparticles (23 nm) were used in our study as model ENs. The effects of ENs on EPS assembly were monitored with dynamic laser scattering (DLS). We found that ENs can induce significant acceleration in Amphora sp. EPS assembly; after 72 hours EN-EPS aggregation reached equilibrium, forming microscopic gels of ∼4–6 µm in size. In contrast, ENs only cause moderate assembly kinetic acceleration for A. angustus and P. tricornutum EPS samples. Our results indicate that the effects of ENs on EPS assembly kinetics mainly depend on the hydrophobic interactions of ENs with EPS polymers. The cycling mechanism of EPS is complex. Nonetheless, the change of EPS assembly kinetics induced by ENs can be considered as one potential disturbance to the marine carbon cycle.
Highlights
Engineered nanoparticles (ENs) are increasingly being developed to improve and innovate industrial and consumer products; for example, they are used to improve semiconductors, sunscreens and cosmetics and in the medicinal industry for imagery and drug delivery [1]
Chemical analysis of exopolymeric substances (EPS) EPS from the three phytoplankton species contained varied protein:carbohydrate ratios, which can be taken as an indicator of their relative hydrophobicity
Of the different EPS used in this study, EPS from A. angustus is the most hydrophobic whilst Amphora EPS is the most hydrophilic
Summary
Engineered nanoparticles (ENs) are increasingly being developed to improve and innovate industrial and consumer products; for example, they are used to improve semiconductors, sunscreens and cosmetics and in the medicinal industry for imagery and drug delivery [1]. As a large fraction of atoms are located at or near their surface, ENs have high electron activities. Cytotoxic interactions between organisms and ENs can occur through various mechanisms such as electro-active groups, heavymetal effects and reactive oxygen species (ROS) [1]. Previous studies have demonstrated the ability of algal and protozoan to uptake ENs [2]. The popularity of ENs in the consumer industry raises critical questions regarding their potential impacts on ecological systems [3], especially in the context of oceanic environments. Any EN-aquatic biota interaction that could alter natural oceanic processes, including the marine carbon cycle or marine food webs, should receive increased attention [4]
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