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Although doping of various rare earth elements such as samarium on zinc oxide nanoparticles (ZnO NPs) can noticeably improve their photocatalytic performance, it may enhance their toxicity to living organisms. Thus, the toxic impacts of samarium-doped ZnO NPs (Sm/ZnO NPs) on different organisms should be carefully evaluated. In this study, an eco-toxicological experimentation system using the green microalga Chlorella vulgaris was established to determine the potential toxicity of ZnO and Sm/ZnO NPs synthesized by polymer pyrolysis method. Accordingly, growth parameters, oxidative stress biomarkers, and morphological features of the algal cells were analyzed. Both ZnO and Sm/ZnO NPs induced a concentration-dependent cytotoxicity by reducing the cell growth, decreasing photosynthetic pigment contents, and causing deformation in the cellular morphology. Moreover, generation of excessive H 2 O 2 , increased activity of superoxide dismutase and ascorbate peroxidase, and reduction in total phenolic and flavonoid contents were observed. Catalase activity was inversely influenced by the NPs in a way that its activity significantly increased at the concentrations of 20 and 25 mg L -1 of ZnO NPs, but was lessened by all supplemented dosages (5-25 mg L -1 ) of Sm/ZnO NPs. Altogether, the obtained results revealed that Sm-doping can play a significant role in ZnO NP-induced toxicity on C. vulgaris cells., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The increased applications of nanomaterials in industry and biomedicine have resulted in a rising concern about their possible toxic impacts on living organisms. It has been claimed that the phytosynthesized nanomaterials have lower toxicity in comparison to their chemically synthesized counterparts. Therefore, it is important to evaluate their toxic effects on the environment. In the present study, we investigated the toxic effects of microwave-synthesized silver-reduced graphene oxide nanocomposites (MS-Ag-rGO) on Chlorella vulgaris . Algal cells were treated by 1, 2, 4 and 6 mg L -1 MS-Ag-rGO for 24 h. The obtained data with three replicates were examined using analysis of variance. Analysis of different growth parameters revealed that MS-Ag-rGO possessed significant dose-dependent toxic effect on C. vulgaris . Scanning electron microscope and fluorescence microscope images of the treated cells established morphological shrinkages and alteration in position of nucleoli. Moreover, reduction in the phenol and flavonoid contents, enhancement of H 2 O 2 content, changes in the antioxidant enzymes activity and decreases in the growth parameters as well as photosynthetic pigments quantities confirmed the toxicity of MS-Ag-rGO to the C. vulgaris cells. Our findings revealed that MS-Ag-rGO possessed higher toxicity on C. vulgaris than Ag-rGO synthesized by hydrothermal technique.

Green algae are dominant primary producers in aquatic environments. Thus, assessing the influences of pollutants such as nanoparticles on the algae is of high ecological significance. In the current study, cadmium selenide nanoparticles (CdSe NPs) were synthesized using the hydrothermal method and their characteristics were determined by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FT-IR) techniques. Subsequently, the toxicity of synthesized nanoparticles on the green microalga Chlorella vulgaris was investigated. The observations by SEM confirmed that exposure to CdSe NPs had severe impacts on the algal morphology. Furthermore, the obtained results revealed the toxic effect of CdSe NPs by a decrease in the number of cells. Measurement of antioxidant enzymes activity showed an increase in the activity of catalase, and a decrease in the activity of superoxide dismutase (SOD) at high concentrations of CdSe NPs. The exposure of C. vulgaris to CdSe NPs resulted also in a change in algal pigments as well as total phenol content. Taken together, CdSe NPs appeared to have significant cytotoxic effects on C. vulgaris in the applied concentrations.

Although vanadium-based nanomaterials have found extensive use in industry, their influence on ecosystems and living organisms is not yet well investigated. In this study, hydrothermal methods were utilized for the synthesis of vanadium pentoxide nanoparticles (V2O5 NPs). The gained NPs were characterized using XRD, FT-IR, EDS, DLS, SEM and TEM techniques. Subsequently, the toxic effects of V2O5 NPs on the model green microalgae Chlorella vulgaris were evaluated. According to the obtained results, V2O5 NPs caused a significant reduction in cell number and biomass production of algae in a dose and time dependent manner. Moreover, flow cytometric analysis confirmed a reduction in the quantity of living cells. Scanning electron microscopy showed plasmolysis and deformation of the cells after exposure to nanoparticles. The photosynthetic pigments and phenolics content exhibited a decrease in comparison with the control sample. Although, non-enzymatic antioxidant system in C. vulgaris displayed an average action, antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) showed a dose dependent increasing trend. These intercellular reactions designated the activation of the antioxidant defense system in response to the induced oxidative stress by V2O5 NPs. [ABSTRACT FROM AUTHOR]