Interactions of CuO nanoparticles with the algae Chlorella pyrenoidosa: adhesion, uptake, and toxicity

Abstract

The potential adverse effects of CuO nanoparticles (NPs) have increasingly attracted attention. Combining electron microscopic and toxicological investigations, we determined the adhesion, uptake, and toxicity of CuO NPs to eukaryotic alga Chlorella pyrenoidosa. CuO NPs were toxic to C. pyrenoidosa, with a 72 h EC50 of 45.7 mg/L. Scanning electron microscopy showed that CuO NPs were attached onto the surface of the algal cells and interacted with extracellular polymeric substances (EPS) excreted by the organisms. Transmission electron microscopy (TEM) showed that EPS layer of algae was thickened by nearly 4-fold after CuO NPs exposure, suggesting a possible protective mechanism. In spite of the thickening of EPS layer, CuO NPs were still internalized by endocytosis and were stored in algal vacuoles. TEM and electron diffraction analysis confirmed that the internalized CuO NPs were transformed to Cu2O NPs (d-spacing, ∼0.213 nm) with an average size approximately 5 nm. The toxicity investigation demonstrated that severe membrane damage was observed after attachment of CuO NPs with algae. Reactive oxygen species generation and mitochondrial depolarization were also noted upon exposure to CuO NPs. This work provides useful information on understanding the role of NPs-algae physical interactions in nanotoxicity.

Influence of Speciation of Thorium on Toxic Effects to Green Algae Chlorella pyrenoidosa

“…In this study, the heteroagglomeration between the precipitation of Th(OH) 4 and algae cells could possibly lead to a reduction in the light available to cells and thus decrease the chlorophyll contents. On the other hand, it might be a mechanism of egodefence that the exposed cells aggregated together to decrease the physical contact with Th, as reported by Zhao et al [21], who showed that the aggregated algae cells act as a barrier to prevent the direct damage of CuO NPs to the cell wall and membrane.…”

“…The TEM images show that nano-sized Th(OH) 4 was deposited both inside and outside the cells. Recent progresses in the aquatic toxicity of engineered nanomaterials suggest that insoluble nano-sized particles might exhibit toxicity to green algae by the following processes: (1) the shading effect may attenuate the photosynthesis by reducing light transmittance; (2) the heteroagglomeration and physical interaction may lead to the internalization of nanoparticles, cell membrane disruption and endocyte outflow; (3) the permeation and entry of nanoparticles into the cells may induce the elevation of intracellular ROS levels and the membrane lipid peroxidation [19,20,21,24,25,26]. All these processes might contribute to the toxic effects of Th to C. pyrenoidosa .…”

Influence of Speciation of Thorium on Toxic Effects to Green Algae <em>Chlorella pyrenoidosa</em>

“…In this study, the heteroagglomeration between the precipitation of Th(OH)4 and algae cells could possibly lead to a reduction in the light available to cells and thus decreasing the chlorophyll contents. On the other hand, it might be a mechanism of egodefence that the exposed cells aggregated together to decrease the physical contact with Th, as reported by Zhao et al [26] that the aggregated algae cells acting as a barrier to prevent the direct damage of CuO NPs to the cell wall and membrane . Figure 5G and I are higher magnification of the areas marked by the black boxes in Figure 5H.…”

“…The TEM images show that nano-sized Th(OH)4 was deposited both inside and outside the cells. Recent progresses in the aquatic toxicity of engineered nanomaterials suggest that insoluble nano-sized particles might exhibit toxicity to green algae by the following processes: (1) the shading effect may attenuate the photosynthesis by reducing light transmittance; (2) the heteroagglomeration and physical interaction may lead to the internalization of nanoparticles, cell membrane disruption and endocyte outflow; (3) the permeation and entry of nanoparticles into the cells may induce the elevation of intracellular ROS levels and the membrane lipid peroxidation [24][25][26][29][30][31]. All these processes might contribute to the toxic effects of Th to C. pyrenoidosa.…”

Mechanism, of Biophysicochemical Interactions and Cellular Uptake at the Nano-Bio Interface: A Review

“…Graphene -a two-dimensional single-atom-thick nanomaterial with unique structural, mechanical and electronic properties has potential biomedical applications [52][53][54]. Its high specific surface area allows high-density biofunctionalization for nanotechnology-based drug delivery [55][56][57]. Furthermore, its smooth, contiguous topography and bio-persistence play a unique role in foreign-body-induced carcinogenesis and tumor progression [58,59].…”