Multiple physiological response analyses of Chlorella vulgaris exposed to silver nanoparticles, ciprofloxacin, and their combination.

This article investigates the individual and combined toxicity of silver nanoparticles (AgNPs) and ciprofloxacin (CIP), a broad-spectrum antibiotic, on the freshwater green microalga *Chlorella vulgaris*. The study found that AgNPs exhibited higher toxicity than CIP, with median effect concentrations (EC50-96h) of 132 µg L⁻¹ and 7,000 µg L⁻¹, respectively, while their mixture showed synergistic toxicity with an EC50-96h of 452 µg L⁻¹. Exposure to these contaminants affected algal growth rate, cell size, photosynthetic pigments, biochemical composition (proteins, lipids, carbohydrates), antioxidant enzyme activities (catalase and glutathione S-transferase), and induced oxidative stress as indicated by increased malondialdehyde levels. The findings highlight that combined exposure to AgNPs and CIP at environmentally relevant concentrations poses enhanced ecotoxicological risks to aquatic primary producers, emphasizing the need to consider mixture effects in environmental risk assessments.