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The uptake and toxicity of silver nanoparticles in Choanoflagellates

By Adam Davis

Abstract

Silver nanoparticles are currently being widely used for a variety of applications, primarily for their novel biocidal properties. Upon release into the environment silver nanoparticles have the potential to be highly toxic towards a range of microorganisms. Choanoflagellates are a filter feeding bacteriovore protozoa which occupy a niche in the microbial loop. Choanoflagellates have previously been shown capable to ingesting sub-micron particles, however little information is known about whether the cells are capable of assimilating manufactured nanoparticles released into the environment. In this study citrate capped silver nanoparticles with a core size of 20 nm were synthesised using a chemical reduction method. The particles were characterised using a multi-method approach both as synthesised and in the presence of the Choanoflagellate’s culture medium (Pratt’s medium). At 5.5 mg/L in Pratt’s medium the nanoparticles were found to be stable over 24 hrs, whilst at 11 μg/L the z average diameter increased to 442 nm as measured by DLS. The Choanoflagellates cells were exposed to various concentrations of silver nanoparticles in medium. Reflectance confocal microscopy was then used to image the uptake of these particles into the Choanoflagellate cells. Silver nanoparticles were found ingested by the Choanoflagellate cells at concentrations as low as 11 μg/L when incubated in nanoparticle suspension for 24 hrs. Using phase contrast microscopy the toxicity of particles washed via ultrafiltration and unwashed particles was then examined. Non washed particles were found to be significantly more toxic than those which had been ultrafiltrated

Topics: GE Environmental Sciences
Year: 2013
OAI identifier: oai:etheses.bham.ac.uk:4111

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