Modulation of the uptake and toxicity of PFOA by Polystyrene and Titanium dioxide nanoparticles in Pacific oysters (Magallana gigas) and Daphnia (Daphnia magna)
Creators: Farajizadeh, Arian
Publisher: name: University of Alberta Library
Year: 2023

<p>Nanomaterial toxicity is a major concern in today’s world. The benefits of nanoparticle use have led to the production of various kinds of nanomaterials including a high volume of nanoplastics, TiO2 nanoparticles, and CeO nanoparticles. Different nanomaterials are shown to be a suitable vector for various toxicants. The effects of plastic pollution on marine organisms are of growing concern. The hydrophobic surface of plastics has been shown to adsorb phenanthrene and increase the rate of uptake into fish. To date, the potential for other nanoparticles to associate with POPs in water and affect POP transport has not been investigated. Titanium dioxide (TiO2) nanoparticles are known to form different eco-coronas by adsorption of various constituents in water. Therefore, I hypothesized that the presence of nano-sized plastic particles could also enhance PFOA uptake in animals. I measured the uptake rate of 14C-PFOA in juvenile Pacific Oysters at different concentrations, and in different periods of exposure time, and investigated whether different concentrations of either 500 nm or  20 nm polystyrene nanoparticles (PS-NPs) altered the uptake rate of PFOA. My results demonstrate that PS-NPs have both a high sorption capacity for PFOA and also can significantly enhance the uptake of PFOA at environmentally realistic exposure concentrations. I found that PFOA uptake at 100 μg/l was increased 2.3-fold in the presence of 1000 µg/L 500 nm PS-NPs and 3.2 -fold increase was seen in the presence of 1000 µg/L 20 nm PS-NPs.  Based on the previous data, I also hypothesized that PFOA would adsorb to the hydrophobic surface of nano sized TiO2 particles and affect the uptake of PFOA into Daphnia magna. I measured the accumulation of PFOA and TiO2 compound in Daphnia using a radiotracer-based method involving 14C-labelled PFOA over multiple concentrations, flux times, and different TiO2 particle sizes. My results showed that TiO2 NPs have a high sorption capacity for PFOA and also meaningfully modulate PFOA uptake at environmentally relevant concentrations. Uptake of 10 μg/L PFOA was found to be 45% higher in the presence of 500 µg/L 5 nm TiO2 which is 20% higher than the uptake enhancement caused by adsorption of PFOA to the 25 nm TiO2, respectively. Results from my uptake experiments demonstrated the exacerbated uptake rate of PFOA by adsorption onto the surface of the plastic and TiO2 nanoparticles in two different organisms. Furthermore, I investigated whether the presence of the NP potentiated accumulation of PFOA, which would result in an intensified PFOA-induced toxicological impact on aquatic animals. PFOA is shown to induce oxidative stress and alter the metabolism of various organisms. I showed that the presence of PS-NPs increased the oxidative stress induced by 1 mg/L PFOA by 2.5-fold and 3-fold in the presence of either 100 mg/L 500 or 20 nm PS-NPs, respectively. These findings demonstrate that micro and nanoplastics as co-contaminants in marine Pacific Oysters can significantly potentiate organic contaminate uptake and toxicity. Additionally, PFOA sorption to TiO2 NPs also potentiated the decrease in metabolic oxygen consumption (MO2) by 0.31-fold, compared to PFOA alone, when co-contaminated with 5nm TiO2 particles. These results also showed for the first time that TiO2 nanoparticles can act as vectors for organic pollutants and significantly modulate their accumulation and toxicity in Daphnia. Overall, my data demonstrated the nanoparticles&#39; capacity to adsorb organic pollutants and showed that adsorption of POPs to NPs accelerated the uptake of organic toxicants and intensified the toxicity of the accumulated toxicant in different aquatic organisms.</p>