Mechanism of nanotoxicity in Chlorella vulgaris exposed to zinc and iron oxide

Pallavi Saxena; Vinod Saharan; Prabhat Kumar Baroliya; Vinod Singh Gour; Manoj Kumar Rai; Harish

doi:10.1016/j.toxrep.2021.03.023

Mechanism of nanotoxicity in Chlorella vulgaris exposed to zinc and iron oxide

Toxicol Rep. 2021 Apr 1:8:724-731. doi: 10.1016/j.toxrep.2021.03.023. eCollection 2021.

Authors

Pallavi Saxena¹, Vinod Saharan², Prabhat Kumar Baroliya³, Vinod Singh Gour⁴, Manoj Kumar Rai⁵, Harish¹

Affiliations

¹ Plant Biotechnology Laboratory, Department of Botany, Mohanlal Sukhadia University, Udaipur, 313 001, Rajasthan, India.
² Department of Molecular Biology and Biotechnology, Rajasthan College of Agriculture, Maharana Pratap University of Agriculture and Technology, Udaipur, 313 001, Rajasthan, India.
³ Department of Chemistry, Mohanlal Sukhadia University, Udaipur, 313 001, Rajasthan, India.
⁴ Amity Institute of Biotechnology, Amity University Rajasthan, Jaipur, India.
⁵ Department of Environmental Science, Indira Gandhi National Tribal University, Amarkantak, Madhya Pradesh, 484887, India.

Abstract

Usage of nanoparticle in various products has increased tremendously in the recent past. Toxicity of these nanoparticles can have a huge impact on aquatic ecosystem. Algae are the ideal organism of the aquatic ecosystem to understand the toxicity impact of nanoparticles. The present study focuses on the toxicity evaluation of zinc oxide (ZnO) and iron oxide (Fe₂O₃) nanoparticles towards freshwater microalgae, Chlorella vulgaris. The dose dependent growth retardation in Chlorella vulgaris is observed under ZnO and Fe₂O₃ nanoparticles and nanoform attributed more toxicity than their bulk counterparts. The IC₅₀ values of ZnO and Fe₂O₃ nanoparticles was reported at 0.258 mg L^-1 and 12.99 mg L^-1 whereas, for the bulk-form, it was 1.255 mgL^-1 and 17.88 mg L^-1, respectively. The significant decline in chlorophyll content and increase in proline content, activity of superoxide dismutase and catalase, indicated the stressful physiological state of microalgae. An increased lactate dehydrogenase level in treated samples suggested membrane disintegration by ZnO and Fe₂O₃ nanoparticles. Compound microscopy, scanning electron microscopy and transmission electron microscopy confirm cell entrapment, deposition of nanoparticles on the cell surface and disintegration of algal cell wall. Higher toxicity of nanoform in comparison to bulk chemistry is a point of concern.

Keywords: ANOVA, analysis of variance; Algae; Antioxidant; Aquatic-ecosystem; BG-11, blue green-11; BSA, bovine serum albumin; CAT, catalase; CDH, central drug house; DDW, double distilled water; FTIR, fourier-transform infrared spectroscopy; Fe2O3, ferric oxide; IC50, half maximal inhibitory concentration; JCPDS, Joint Committee on Powder Diffraction Standards; LDH, lactate dehydrogenase; MDA, malondialdehyde assay; NADH, nicotinamide adenine dinucleotide (reduced form); NCBI, national center for biotechnology information; NPs, nanoparticles; Nanoparticles; OD, optical density; PBS, phosphate-buffered saline; PDI, polydispersity index; ROS, reactive oxygen species; SD, standard deviation; SEM, scanning electron microscopy; SOD, superoxide dismutase; Stress; TEM, transmission electron microscopy; UV, ultra violet; XRD, X-ray diffraction; ZnO, zinc oxide.