Effect of selenium nanoparticles induced toxicity on the marine diatom Chaetoceros gracilis

Discharge of nanomaterials into the environment contributes to a diverse group of pollutants. In the present study, the toxicity of selenium nanoparticles (SeNPs) on the marine diatom Chaetoceros gracilis was studied in the laboratory by conducting 96 h toxicity experiments. The SeNPs were synthesized by reducing sodium selenite using L-cysteine and characterized by spectroscopic and microscopic techniques. X-ray photoelectron spectroscopic (XPS) data showed a distinctive selenide peak at 56 eV, indicating the oxidation states Se3d3/2 and Se3d5/2. Raman spectra results indicated the characteristic A1 and S mode of selenium (Se). Growth inhibitory experiments were performed (LC50 14.63 mg/L) for 96 h using various concentrations of SeNPs and its membrane damage to cells was observed. Upon treatment with SeNPs, an increased percentage of reactive oxygen species (ROS) production was detected from 28.77±3.13% to 130.55±3.16% after 96 h. Malonaldehyde (MDA), a biomarker of lipid peroxidation was quantified and exposure to 50 mg/L of SeNPs significantly (p < 0.05) increased MDA concentration from 4.31±0.02 to 5.05±0.05 µM in 96 h. The morphological distortion, including cell wall damage, that affects the cellular integrity upon exposure to SeNPs was evident from microscopic studies. These results clearly indicate that, even at lower concentrations, SeNPs toxicity on lower trophic organisms is significant enough to cause cellular level alterations.