Comparative study on the toxicity of biosynthesized and chemically synthesized gold nanoparticles

There has been a rush into the green synthesis of nanoparticles in recent years. However, the direct comparison of the toxicity of biosynthesized nanoparticles and chemically synthesized nanoparticles was seldom reported. Herein, a green route for the synthesis of gold nanoparticles (Bio-AuNPs) was developed by incubation of gold precursors with Oocystis sp. algal extract. The toxicity of Bio-AuNPs and citrate-stabilized AuNPs (Chem-AuNPs) was further compared by using another microalgae Chlorella vulgaris and its higher trophic level Daphnia magna as the model organisms. The exposure of Chem-AuNPs induced the aggregation of algal cells and dramatically inhibited the growth of C. vulgaris at 5 mg/L, while no significant inhibitory effect was observed for Bio-AuNPs at 20 mg/L. Additionally, the 24 and 48 h LC 50 of Bio-AuNPs to D. magna were much higher than those of Chem-AuNPs. The data directly demonstrated that Bio-AuNPs have better biosafety than Chem-AuNPs, making them potentially useful in biomedical fields and cancer therapy and diagnosis. Graphical Abstract