Toxic Effects of Colloidal Silver Particles Biosynthesized using Gamma-irradiated Propolis Extract and Silver Nitrate Salts on Microalgae Chlorella vulgaris

The discharge of nanoparticles, including silver nanoparticles used in various industries into the environment, and their potential toxic effects on plants, animals and humans has raised global concerns, highlighting the need for more research on this topic. The aim of this study was to investigate the toxicity of silver nitrate salt (AgNO3), γ-irradiated (10 kGy) (AgNPs-γ) and non-irradiated (AgNPs) silver particles synthesized by the alcoholic extract of bee propolis at different concentrations (10, 50, 100, 200 μg/l) on Chlorella vulgaris microalgae. The results demonstrated that exposure to AgNPs-γ and AgNPs and silver nitrate salts increased growth inhibition (%) in a dose-dependent manner (P<0.05). Moreover, cell viability (VC %), microalgal cell density/biomass (μ/L) and chlorophyll-a concentration decreased. In contrast, electrolyte conductivity/living cells (electrolyte leakage (EL %) increased in the exposed groups, compared with the control group (P<0.05). These results showed the following trend in inducing toxicity, inhibiting growth and photosynthesis in Chlorella vulgaris: AgNO3 < AgNPs < AgNPs-γ.