Cellular accumulation and cytotoxic effects of zinc oxide nanoparticles in microalga Haematococcus pluvialis

Abstract

Background Zinc oxide nanoparticles (ZnO NPs) are widely used in household and cosmetic products which imply an increased releasing of these particles into the environment, especially aquatic ecosystems, resulting in the need of assessing the potential toxic effects of ZnO NPS on the aquatic organisms, particularly on microalgae which form the base for food chain of aquatic biota. The present study has investigated the dose- and time-dependent cellular accumulation and the corresponding cytotoxic effects of increasing concentrations of ZnO NPs from 10–200 μg/mL on microalga Haematococcus pluvialis at an interval of 24 h for 96 h. Methods The scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) was used to qualitatively detect the cellular accumulation of ZnO NPs in algal cells, while inductively coupled plasma optical emission spectrometry (ICP OES) was performed to quantify the cell associated-zinc in algal cells. The percentage of cell death, reduction in algal biomass, and loss in photosynthetic pigments were measured to investigate the cytotoxic effects of ZnO NPs on H. pluvialis. Extracellular and intracellular changes in algal cells resulted from the treatment of ZnO NPs were demonstrated through optical, scanning, and transmission electron microscopic studies. Results SEM-EDX spectrum evidenced the accumulation of ZnO NPs in algal biomass and ICP OES results reported a significant (p < 0.05) dose- and time-dependent accumulation of zinc in algal cells from 24 h for all the tested concentrations of ZnO NPs (10–200 μg/mL). Further, the study showed a significant (p < 0.05) dose- and time-dependent growth inhibition of H. pluvialis from 72 h at 10–200 μg/mL of ZnO NPs. The morphological examinations revealed substantial surface and intracellular damages in algal cells due to the treatment of ZnO NPs. Discussion The present study reported the significant cellular accumulation of ZnO NPs in algal cells and the corresponding cytotoxic effects of ZnO NPs on H. pluvialis through the considerable reduction in algal cell viability, biomass, and photosynthetic pigments together with surface and intracellular damages.

Investigating the Internalization and COVID-19 Antiviral Computational Analysis of Optimized Nanoscale Zinc Oxide

“…A significant ≈3-fold increase of MFI was observed by increasing the concentration of ZnO NPs from 40 to 80 μg/mL ( p < 0.05) (Figure b). A similar concentration-dependent uptake was previously observed. , …”

“…A similar concentration-dependent uptake was previously observed. 60,61 ■ CONCLUSIONS Based on their great premises, ZnO NPs were successfully synthesized with a high degree of purity and crystallinity by tuning zinc precursor concentration, reaction pH, and stirring speed. The optimized ZnO NPs had a crystallite size of 11.50 ± 0.71 nm with an identical hexagonal wurtzite P63mc crystal structure.…”

A Review on Haematococcus pluvialis Bioprocess Optimization of Green and Red Stage Culture Conditions for the Production of Natural Astaxanthin

“…However, higher concentrations of the metals NPs may lead to toxic effects, resulting in the cell density of H. pluvialis significantly decreasing, due to its restriction on the microalgae for the light accessibility and finally disturbing the photosynthesis process. Similarly, Djaeramane et al [ 74 ] reported that the treatment of ZnO NPs on H. pluvialis at the concentration of 10–200 μg mL −1 resulted in the reduction on the cell viability, biomass, and photosynthetic pigments together with surface and intracellular damages. In other microalga systems, Sibi et al [ 78 ] showed that by increasing the CuNPs, Pb-NPs, Zn NPs, and Mg-NPs concentrations in the growth media, the specific growth rate and biomass density of Chlorella vulgaris were significantly decreased.…”

“…Recently, the potential application of metal-based nanoparticles (NPs) has been attracting applications in the cultivation of plant and algae. Multiple studies revealed the positive effects of metal-based NPs on certain algae when appropriate concentrations were applied to the cultures [ 74 , 75 ]. He et al [ 76 ] showed that the cell density and chlorophyll content were enhanced at 20 mg L −1 supplementation of Fe 2 O 3 NPs in the growth medium of Scenedesmus obliquus .…”

Changes of Carotenoids in Haematococcus pluvialis with the Presence of Light Metals

“…The accumulate in of carotenoids reduces the oxidative stress by quenching the reactive oxygen species (ROS) and free radicals. The presence of metals in the environment, especially heavy metals lead to the increase of oxidative stress (AYDOÐAN et al, 2017;Djearamane et al, 2020).…”