Exposure matters: effects of environmentally realistic exposure conditions on toxicity of model nanomaterials to Daphnia Magna

Abstract

Nanomaterials (NMs) can be defined as having at least one external dimension between 1-100nm. Due to their small size, NMs have a large surface area giving them characteristics that differ from bulk material. NMs are incorporated into numerous applications making environmental exposure to NMs likely. Increased reliance on plastic results in accumulation of nano-plastics in fresh waters. Polystyrene (PS) acts as a representative of both nano-plastic and NMs. The deposition of gold (Au) NMs is also likely due to their use in medical applications so that both PS and Au have a potential to interact with environmental organisms. Daphnia manga (D. magna) is an ideal candidate in fresh water toxicity testing. Toxicity, uptake and retention of NMs by organisms is dependent on several factors such as NM charge, shape, chemical composition and the absorption of natural biomolecules binding to the surface of the NM creating an eco-corona, altering stability of the NMs thereby changing their toxicity. This work investigates the toxicity of PS and Au NMs and explores the effects of charge, shape, presence of a corona and the impact of realistic modes of presentation of NMs to D. magna and how these factors impact toxicity, uptake, retention and depuration