Evaluating the toxicity of engineered nanoparticles to Australian freshwater biota
Creators: name: Lekam Ralalage, Sam
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 4104
subject: Environmental management
classificationCode: 410402
subject: Environmental assessment and monitoring
classificationCode: 410404
subject: Environmental management

description: Nanotechnology is a fast-growing industry yielding many benefits to society with various types of nanoparticles (NPs) used in numerous applications. Intensive manufacture of NPs started in 1980s and these materials are being increasingly used in consumer products. However, there is also increasing concern regarding their potential impacts on biota in the environment since the release of NPs to the ecosystems is increasing. Aquatic environments are particularly at risk since considerable amounts of NPs may eventually end up in water bodies causing direct and indirect effects on aquatic organisms and could transfer up trophic chains. However, currently there are very few techniques that can measure the quantity of NPs released into aquatic and terrestrial environments which makes it difficult to predict their effects on organisms. Though NP size remains central to determining toxicity, studies suggest that other inherent factors like coating agents should be considered in toxicity studies. Little is known about the transformation and stability of NPs in the environment and the effects of aged NPs on organisms compared with their pristine forms. In the current PhD project, how surface coatings influence the toxicity of NPs to selected aquatic organisms, their uptake through the trophic chain and their toxicity with ageing were investigated using standard toxicity tests, bioassays and fate and behaviour assessment of NPs in media. Four freshwater organisms; Hydra vulgaris, Raphidocelis subcapitata, Daphnia carinata and Paratya australiensis which represent different trophic levels were used to evaluate the toxicity of silver NPs (AgNPs) coated with three different ligands; Tyrosine-coated (T-AgNP), Epigallocatechin gallate-coated (E-AgNP) and Curcumin-coated (C-AgNP) AgNPs. These AgNPs were produced, characterized, and their stability was assessed in relevant media as representative of acute toxicity and ageing experiments. Organisms cultured in the laboratory or collected from the field were exposed to the AgNPs and their effects were assessed using several endpoints. The results generated from this research are presented and compared with published data from literature. From the study, it was found that the effects of AgNPs were dependent on several factors; the surrounding medium, ageing and type of coating all influenced the transformation and stability of NPs. Coating and dose-dependent morphological, behavioural, acute and sub-lethal effects on the organisms were observed. Differences in sensitivity and response among different organisms in the end-points tested were observed. Organisms also responded differently when exposed to aged AgNPs; compared with exposure to their pristine forms. The findings from this study will contribute to a better understanding of the potential risks of differently coated AgNPs to organisms in the freshwater environment.