Chronic exposure of the freshwater alga Pseudokirchneriella subcapitata to five oxide nanoparticles: Hazard assessment and cytotoxicity mechanisms

Abstract

The increasing use of nanoparticles (NPs) unavoidably enhances their unintended introduction into the aquatic systems, raising concerns about their nanosafety. This work aims to assess the toxicity of five oxide NPs (Al 2 O 3 , Mn 3 O 4 , In 2 O 3 , SiO 2 and SnO 2) using the freshwater alga Pseudokirchneriella subcapitata as a primary producer of ecological relevance. These NPs, in OECD medium, were poorly soluble and unstable (displayed low zeta potential values and presented the tendency to agglomerate). Using the algal growth inhibition assay and taking into account the respective 72 h-EC 50 values, it was possible to categorize the NPs as: toxic (Al 2 O 3 and SnO 2); harmful (Mn 3 O 4 and SiO 2) and non-toxic/non-classified (In 2 O 3). The toxic effects were mainly due to the NPs, except for SnO 2 which toxicity can mainly be attributed to the Sn ions leached from the NPs. A mechanistic study was undertaken using different physiological endpoints (cell membrane integrity, metabolic activity, photosynthetic efficiency and intracellular ROS accumulation). It was observed that Al 2 O 3, Mn 3 O 4 and SiO 2 induced an algistatic effect (growth inhibition without loss of membrane integrity) most likely as a consequence of the cumulative effect of adverse outcomes: i) reduction of the photosynthetic efficiency of the photosystem II (Ф PSII); ii) intracellular ROS accumulation and iii) loss of metabolic activity. SnO 2 NPs also provoked an algistatic effect probably as a consequence of the reduction of Ф PSII since no modification of intracellular ROS levels and metabolic activity were observed. Altogether, the results here presented allowed to categorize the toxicity of the five NPs and shed light on the mechanisms behind NPs toxicity in the green alga P. subcapitata.

Rapid In Situ Biomonitoring of Subsoil Contamination by Applying an Algae-Soaked Disc Seeding Assay

“…Damage of membrane integrity and disturbance of electron and ion transport chains of the cell membrane after the attachment of nanomaterials has been regarded as increase of membrane permeability [35]. Decrease of esterase activity has been recognized as a reduction of metabolic activity in algal cells [36]. In AgNP-treated soils, NPs themselves or silver ions dissolved from the NPs may respond to exposed algal cell walls, thereby increasing cell size.…”

Mathematical Modeling Approaches for Assessing the Joint Toxicity of Chemical Mixtures Based on Luminescent Bacteria: A Systematic Review

“…The functions of the cell membrane are considered in many aspects, such as transmembrane transport of small molecules, energy exchange, cell recognition, cell-mediated immunity, nerve conduction and metabolism regulation and so on (Oxender and Fox, 1978 ; Alberts et al, 1989 ). The impact of NPs on the membrane or wall integrity of algal cells (Angel et al, 2015 ; Sendra et al, 2017 ; Sousa et al, 2019 ) and bacteria cells (Kaweeteerawat et al, 2015 ; Martín-de-Lucía et al, 2017 ; Pulido-Reyes et al, 2017 ) ( Figure 7A ), has been evaluated extensively. Indications of damaged cell membrane make it interesting to study the potential biotoxicity effect of multi-component mixtures.…”

Facile preparation of zinc nanoparticles mediated by plant aqueous extract and assessment of the antioxidant, cytotoxicity and anti‐human bone carcinoma properties

“…Superoxide radical is formed by a reduction reaction of oxygen molecule. This reaction can be done as a result of the redox cycle, or enzymatically with the catalysis of NADPH oxidase, and also as a byproduct of enzymatic reactions with Xanthine oxidase and a byproduct of the electron transport chain in mitochondria [22,[25][26][27]. By upregulating the xanthine oxidase and NADPH oxidase enzymes, nanomaterials increase the production of superoxide radicals in some cells such as macrophages and neutrophils and trigger inflammatory reactions.…”

“…For example, Zn nanoparticles used in sunscreens produce singlet oxygen and superoxide under the influence of light rays. An increase in the level of ROS leads to inflammatory responses such as an increase in cells with polymorphous nuclei and disturbances in the phago-cytosis process of macrophages in some model animals such as rodents [22,[25][26][27]. Oxidative stress is caused by the predominance of free radicals on antioxidants and is one of the main mechanisms of toxicity of most metal nanoparticles such as gold, zinc, iron and silver [25][26][27][28].…”