Bacteria and fullerene: The microbial response to fullerene water suspensions
Lyon, Delina Yvonne-Marie de Souza
Alvarez, Pedro J.
Doctor of Philosophy thesis
The current nanotechnology boom necessitates timely research into the health and environmental impacts of nanomaterials to enhance their eco-responsible manufacture, use, and disposal. Using the water-insoluble C60 as a model nanomaterial, the potential environmental impacts of a C60 water suspension, termed nC60, are here assessed with bacteria as a receptor. nC60 was evaluated for antibacterial activity, antibacterial mechanisms, impact on natural microbial systems, and potential disinfection applications. nC60 is a potent antibacterial agent when tested against pure cultures of different bacteria. Whereas neither light nor oxygen affects its potency, toxicity is increased by smaller particle size and mitigated by salts which promote precipitation. In complex environments, toxicity was lessened by salts or by natural organic matter that sorbed or coated nC60, reducing its bioavailability. The applicability of nC60 as a disinfectant is thus limited to situations with limited organic matter and debris (e.g., drinking water disinfection); it is not recommended for antibiofouling coatings where precipitating debris occluded the nC60 coating and promoted biofilm formation. In contrast to literature showing nC60 -generated reactive oxygen species damaging eukaryotic systems, this research shows that nC60 behaves as an oxidant upon direct contact with the cell, leading to uncoupled respiration and/or damaged respiratory proteins. The methods that were previously used to detect ROS-mediated damage are shown to be ambiguous and susceptible to interference by nC60, implying that the evidence of ROS-mediated oxidative stress needs to be re-evaluated. Overall, this research reflects an overall image of preventable or negligible environmental impact of nC60, and provides a methodology by which the potential environmental impacts of other nanomaterials can be evaluated.