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Title: Characterisation of engineered nanoparticles and their interaction with natural biological and non-biological material
Author: Taylor, Cameron S.
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2014
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Form, mobility, toxicity and the eventual fate of engineered nanomaterials in environmental ecosystems are currently not well defined and are needed to improve risk assessment and legislation. The present study subjected uncoated zinc oxide (ZnO) nanoparticles (30nm and 200nm) and coated silver (Ag) nanoparticles (Paraffin: 3-8nm and citrate/PVP: 50nm) to different ionic strength media and different types of algal/bacterial extracellular-polymeric species (EPS) at long (6 months) and short (2 weeks) timescales. Changes in particle size distribution and stability were examined using a multi-method approach. Sample concentration and sample polydispersity are important factors when selecting techniques. Uncoated ZnO nanoparticles aggregated heavily in water at high concentrations (1000mg/L). However silver nanoparticles (1-10mg/L) remained stable at all ionic strengths and EPS in this study due to the steric component of their coatings. Nano-toxicological experiments involving cyanobacteria S.leopoliensis and green algae C.reinhardtii showed size-dependent toxicity from coated nanosilver particles. Smaller nanoparticles (3-8nm) showed greater dissolution over 72h and greater toxicity to both species than 50nm particles indicating silver ions are an important toxicity mechanism. Nanoparticle coatings were likely important in controlling dissolution levels. Cell viability and production of reactive oxygen species (ROS) were shown to be important mechanisms of toxicity to phycological species. Species specific effects were noted for both silver nanoparticles. EPS from S.leopoliensis were noted to remove ionic silver from suspension and different types of C.reinhardtii EPS were produced when particles underwent different levels of toxic stress indicating that EPS could both affect particle toxicity and be affected by it. This work has demonstrated that coated nanoparticles could remain stable under various ionic strengths and with exposure to algal organic matter for timescales up to 6 months. This could result in adverse effects to aquatic organisms were they to reach environmental systems and is of concern to nanomaterial risk assessors.
Supervisor: Crossley, Alison; Grovenor, Chris Sponsor: NanoFATE EU project
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Materials Sciences ; Ecotoxicology Nanoparticle Characterisation Nanoparticle Fate Nanoparticle Toxicity Algae and Cyanobacteria ; Materials ; Stability ; Suspension ; Coatings ; Silver ; Zinc Oxide ; Fate ; Ecotoxicology ; Algae ; Cyanobacteria ; Toxicity ; Reactive Oxygen Species ; Cell Viability ; Extra-cellular Polymeric Species