The stochastic association of nanoparticles with algae at the cellular level: Effects of NOM, particle size and particle shape

Fazel Abdolahpur Monikh,Latifeh Chupani,Zhiling Guo,Peng Zhang,Gopala Krishna Darbha,Martina G Vijver,Eugenia Valsami-Jones,Willie J.G.M Peijnenburg

doi:10.1016/j.ecoenv.2021.112280

Abstract

Association of nanoparticles (NPs) with algae likely plays a critical role in their transfer in aquatic food chains. Although our understanding of the ecotoxicity and fate of NPs in the environment is increasing, it is still unclear how the physicochemical properties of NPs influence their interaction with algae at cellular levels and how this is reflected at a population level. This is due to the limitation in the existing analytical techniques to quantify the association of NPs with cells. To fill this data gap, we applied the novel technique of single-cell inductively coupled plasma mass spectrometry to quantify the cellular association of gold (Au)-NPs with algal cells (Pseudokirchneriella subcapitata) as a function of particle size, shape (spherical 10 nm, spherical 60 nm, spherical 100 nm, rod-shaped 10 × 40 nm, and rod-shaped 50 × 100 nm), and surface chemistry [citrate and natural organic matter (NOM) coating] on a cell-by-cell basis. The association of Au-NPs with algal cells was found to be a random probability following a so-called stochastic process; after 72 h of exposure, less than 45% of the cell population accumulated NPs on their surface. The number of Au-NPs per cell was found to be heterogeneously distributed as some cells were associated with a significantly higher number (e.g. up to 600 spherical 10 nm particles per cell) of Au-NPs than other cells present in the medium. The presence of NOM on the surface of the particles decreased the percentage of cells containing NPs except for the spherical 60 nm Au-NPs. We conclude that some algae within a population can accumulate NPs on their surface and this accumulation is influenced by the size, shape, and surface chemistry of NPs. It is important to understand how NPs may enter aquatic food chains to assess the possible risk.

Highlights

Nanoparticles (NPs) can enter the environment and it is highly likely that they interact with microorganisms such as bacteria and algal cells
This implies that NPs internalization in algae is not the only way through which NPs can enter aquatic food chains, because it is possible that the first consumers digest the accumulated NPs present in the extracellular polymeric substances (EPS) of algal cells
We exposed the algae cells to different numbers of NPs, and this can lead to different uptake in cells as observed in our previous study (Abdolahpur Monikh et al, 2019c), the current study clearly shows that similar algal cells within a single population contain different numbers of particles even when they are exposed for a certain period of time to particles of the same size and shape

Summary

Introduction

Nanoparticles (NPs) can enter the environment and it is highly likely that they interact with microorganisms such as bacteria and algal cells. It is reported that NPs are associated with algal cells and accumulate in their EPS (Chen et al, 2019). This implies that NPs internalization in algae is not the only way through which NPs can enter aquatic food chains, because it is possible that the first consumers digest the accumulated NPs present in the EPS of algal cells. It is of paramount importance to shed light on NPs association with algal cells and the factors influencing this association

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