Influence of Bovine Serum Albumin and Alginate on Silver Nanoparticle Dissolution and Toxicity to Nitrosomonas europaea

• Published in: Environmental science & technology 2013-12, Vol.47 (24), p.14403-14410
• Main Authors: Ostermeyer, Ann-Kathrin, Kostigen Mumuper, Cameron, Semprini, Lewis, Radniecki, Tyler
• Format: Article
• Language: English
• Subjects: Alginates - chemistry; Animals; Applied sciences; Biological and medical sciences; Biological treatment of waters; Biotechnology; Cattle; Dissolution; Environment and pollution; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General purification processes; Glucuronic Acid - chemistry; Gram-negative bacteria; Hexuronic Acids - chemistry; Industrial applications and implications. Economical aspects; Metal Nanoparticles - chemistry; Metal Nanoparticles - toxicity; Nanoparticles; Nitrification - drug effects; Nitrosomonas europaea; Nitrosomonas europaea - drug effects; Pollution; Serum Albumin, Bovine - chemistry; Silver; Silver - chemistry; Silver - toxicity; Solubility; Spectrophotometry, Ultraviolet; Toxicity; Toxicity Tests; Wastewaters; Water treatment and pollution
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es4033106

Bovine serum albumin (BSA), a model protein, reduced the toxicity of 20 nm citrate silver nanoparticles (AgNP) toward Nitrosomonas europaea, a model ammonia oxidizing bacteria, through a dual-mode protection mechanism. BSA reduced AgNP toxicity by chelating the silver ions (Ag+) released from the AgNPs. BSA further reduced AgNP toxicity by binding to the AgNP surface thus preventing NH3-dependent dissolution from occurring. Due to BSA’s affinity toward Ag+ chemisorbed on the AgNP surface, increased concentrations of BSA lead to increased AgNP dissolution rates. This, however, did not increase AgNP toxicity as the dissolved Ag+ were adsorbed onto the BSA molecules. Alginate, a model extracellular polysaccharide (EPS), lacks strong Ag+ ligands and was unable to protect N. europaea from Ag+ toxicity. However, at high concentrations, alginate reduced AgNP toxicity by binding to the AgNP surface and reducing AgNP dissolution rates. Unlike BSA, alginate only weakly interacted with the AgNP surface and was unable to completely prevent NH3-dependent AgNP dissolution from occurring. Based on these results, AgNP toxicity in high protein environments (e.g., wastewater) is expected to be muted while the EPS layers of wastewater biofilms may provide additional protection from AgNPs, but not from Ag+ that have already been released.