The activity of silver nanoparticles against microalgae of the Prototheca genus.

Aim: To investigate the in vitro activity of silver NPs (AgNPs) against pathogenic microalgae of the Prototheca genus. Materials & methods: The antialgal potential of AgNPs against Prototheca species of both clinical and environmental origin was assessed from minimum inhibitory (algistatic) and algicidal concentrations. The in vitro cytotoxicity of AgNPs against bovine mammary epithelial cell line was evaluated by means of the standard MTT assay. Results: AgNPs showed a strong killing activity toward Prototheca algae, as the minimal algicidal concentration (MAC) values matched perfectly the corresponding minimum inhibitory concentration (MIC) values for all species (MAC = MIC, 1-4 mg/l), except P. stagnora (MIC > 8 mg/l). The concentrations inhibitory to pathogenic Prototheca spp. (MIC, 1-4 mg/l) were below the concentrations at which any toxicity in epithelial cells could be observed (CC20 > 6 mg/l). Conclusion: The study emphasizes the potential of AgNPs as a new therapeutic tool for the management of Prototheca infections.