The effect of chitosan-modified gold nanoparticles in Lemna valdiviana and Daphnia pulex

Gold nanoparticles (AuNPs) are nowadays used in many areas of science, particularly in medicine as drug release and gene carriers. The extensive use of these materials makes imperative the study of their effects on the environment after their disposal, that mostly affects the aquatic media. The present work explores the bioaccumulation and toxicity of chitosan-functionalized and non-functionalized gold nanoparticles, with primary producers (Lemna valdiviana) and primary consumers (Daphnia pulex) aquatic organisms. Bioaccumulation of 27.4 nm AuNPs and 43.1 nm chitosan-gold nanoparticles (CO-AuNPs) was evaluated in both microorganisms, finding accumulation of AuNPs and inhomogeneous aggregation of CO-AuNPs in Daphnia pulex gut, and internalization of both types of nanoparticles in Lemna valdiviana cell walls. The effective concentration of nanomaterial for 50% survival (LC50) of Daphnia pulex organisms was 1.13 mg/L for AuNPs and 0.96 mg/L for CO-AuNPs in the acute test. In Lemna valdiviana 7-day test, the EC50 for area and frond number were 1.19 mg/L and 1.26 mg/L, respectively, for AuNPs, 1.53 mg/L and 1.44 mg/L, respectively, for CO-AuNPs, finding higher toxicity of CO-AuNPs to Daphnia pulex, and AuNPs to Lemna valdiviana. The obtained results suggest that the effects of nanomaterials on the growth and survival of key organisms deserve further study, as this may lead to the development of appropriate environmental regulations.