Interactions of engineered nanomaterials with biotic and abiotic factors in an aquatic environment
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Ahmedabad University
Abstract
The enabling power of nanotechnology is based on the use of an engineered material or final product that has at least one dimension within the scale of 1 to 100 nm. Nanomaterials differ from bulk material not only in terms of size and optical properties but also in terms of physical and chemical properties such as composition, shape, surface layer, reactivity and toxicity. Today with more than 1800 nanoproducts in the market, Nanotechnology is anticipated to revolutionize product development and manufacture that could contribute up to three trillion US dollars to the worldwide economy by 2020. The studies on nanomaterials safety in aquatic environment are specifically focused on direct exposure and its effects certain aquatic organisms. There is limited understanding on the interaction of nanomaterials with biotic and abiotic factors and their consequent effects in the food web organisms at cellular and molecular level. The present work has investigated the interaction and effects of most used metal (Ag and QDs) and metal oxide (TiO2 and ZnO) nanoparticles in the aquatic ecosystem. In a food chain based study, it was observed that 65% of the CdTe QDs bioaccumulated in Paramecia when it exposed with 25 µg/mL of QDs in the presence of E. coli cells. A significant loss in bacterivory potential (29%) of Paramecium was observed with a ~12 h of delay in doubling time due to bioaccumulation of QDs. Moreover, the trophic transfer of QDs from E. coli to Paramecium was also observed with 1.4 times higher Cd (207 ± 24 μg/mL
BMF = 1.4) in Paramecia, which indicates to the biomagnification of QDs. The trophic transfer potential of ZnO NPs was also investigated up to three trophic levels in bacteria (E. coli), protozoan (Paramecium) and fish (zebrafish eleutheroembryo). E. coli cells were observed to accumulate 131248 μg/g of Zn upon exposure to 50 μg/mL ZnO NPs with a bioconcentration factor of 7473 mL/g. A biomagnification factor (BMF) of 7.7 was observed in Paramecium cells containing 1014840 μg/g of Zn after feeding on ZnO NPs loaded E. coli cells. However, a BMF of 0.07 was observed in zebrafish eleutheroembryos (at third trophic level) containing 70823 μg/g of Zn after feeding on ZnO NPs loaded Paramecium cells. Additionally, a transcriptomic response of the organisms at each trophic level was determined after exposure with the ZnO NPs. In a predator-prey based microcosm study, the fate of titanium dioxide nanoparticles (nTiO2) was investigated. The results demonstrated that the presence of predator, Paramecium in the microcosm influences the intensity of hetero-agglomeration and co-sedimentation NPs with the prey, E. coli. The extent of agglomeration in the microcosm was in the order: combined E. coli and Paramecium > Paramecium only > E. coli only > without E. coli or Paramecium. The clay minerals are one of the most abundant and ubiquitous abiotic factor in the aquatic environment that possess large surface area and high sorption capacity for chemicals and metals. Hence, we investigated the interactions of ZnO NPs and Ag NPs with the montmorillonite clay and their consequent effects in Tetrahymena pyriformis and zebrafish eleutheroembryos were also determined. The result showed that ZnO NPs forms heteroagglomerates with clay particles that leads to their sedimentation in the aquatic system. The Fourier transform infrared spectroscopy analysis of ZnO NPs-clay association confirmed the interaction ZnO NPs with Si-O-Al region of the clay. Further, the toxicity assessment in Tetrahymena cells showed higher affects of ZnO NPs-clay association as compared to the bare ZnO NPs. Similarly, heteroagglomeration of Ag NPs was also observed with clay minerals at acidic and neutral pH conditions. Additionally, an increased toxicity of Ag NPs-clay association was observed as compared to the bare Ag NPs in the zebrafish eleutheroembryos. In the present work, the understanding made on the eco-bio-compatibility of these novel materials will lead to the development of “safe by design" nanomaterials to harvest the power of this enabling technology, nanotechnology.
BMF = 1.4) in Paramecia, which indicates to the biomagnification of QDs. The trophic transfer potential of ZnO NPs was also investigated up to three trophic levels in bacteria (E. coli), protozoan (Paramecium) and fish (zebrafish eleutheroembryo). E. coli cells were observed to accumulate 131248 μg/g of Zn upon exposure to 50 μg/mL ZnO NPs with a bioconcentration factor of 7473 mL/g. A biomagnification factor (BMF) of 7.7 was observed in Paramecium cells containing 1014840 μg/g of Zn after feeding on ZnO NPs loaded E. coli cells. However, a BMF of 0.07 was observed in zebrafish eleutheroembryos (at third trophic level) containing 70823 μg/g of Zn after feeding on ZnO NPs loaded Paramecium cells. Additionally, a transcriptomic response of the organisms at each trophic level was determined after exposure with the ZnO NPs. In a predator-prey based microcosm study, the fate of titanium dioxide nanoparticles (nTiO2) was investigated. The results demonstrated that the presence of predator, Paramecium in the microcosm influences the intensity of hetero-agglomeration and co-sedimentation NPs with the prey, E. coli. The extent of agglomeration in the microcosm was in the order: combined E. coli and Paramecium > Paramecium only > E. coli only > without E. coli or Paramecium. The clay minerals are one of the most abundant and ubiquitous abiotic factor in the aquatic environment that possess large surface area and high sorption capacity for chemicals and metals. Hence, we investigated the interactions of ZnO NPs and Ag NPs with the montmorillonite clay and their consequent effects in Tetrahymena pyriformis and zebrafish eleutheroembryos were also determined. The result showed that ZnO NPs forms heteroagglomerates with clay particles that leads to their sedimentation in the aquatic system. The Fourier transform infrared spectroscopy analysis of ZnO NPs-clay association confirmed the interaction ZnO NPs with Si-O-Al region of the clay. Further, the toxicity assessment in Tetrahymena cells showed higher affects of ZnO NPs-clay association as compared to the bare ZnO NPs. Similarly, heteroagglomeration of Ag NPs was also observed with clay minerals at acidic and neutral pH conditions. Additionally, an increased toxicity of Ag NPs-clay association was observed as compared to the bare Ag NPs in the zebrafish eleutheroembryos. In the present work, the understanding made on the eco-bio-compatibility of these novel materials will lead to the development of “safe by design" nanomaterials to harvest the power of this enabling technology, nanotechnology.