title: Effects of chloride and ionic strength on physical morphology, dissolution, and bacterial toxicity of silver nanoparticles.
abstract: In this study, we comprehensively evaluate chloride- and ionic-strength-mediated changes in the physical morphology, dissolution, and bacterial toxicity of silver nanoparticles (AgNPs), which are one of the most-used nanomaterials. The findings isolate the impact of ionic strength from that of chloride concentration. As ionic strength increases, AgNP aggregation likewise increases (such that the hydrodynamic radius [HR] increases), fractal dimension (Df) strongly decreases (providing increased available surface relative to suspensions with higher Df), and the release of Ag(aq) increases. With increased Ag(+) in solution, Escherichia coli demonstrates reduced tolerance to AgNP exposure (i.e., toxicity increases) under higher ionic strength conditions. As chloride concentration increases, aggregates are formed (HR increases) but are dominated by AgCl(0)(s) bridging of AgNPs; relatedly, Df increases. Furthermore, AgNP dissolution strongly increases under increased chloride conditions, but the dominant, theoretical, equilibrium aqueous silver species shift to negatively charged AgClx((x-1)-) species, which appear to be less toxic to E. coli. Thus, E. coli demonstrates increased tolerance to AgNP exposure under higher chloride conditions (i.e., toxicity decreases). Expression measurements of katE, a gene involved in catalase production to alleviate oxidative stress, support oxidative stress in E. coli as a result of Ag(+) exposure. Overall, our work indicates that the environmental impacts of AgNPs must be evaluated under relevant water chemistry conditions.
authors: Department of Civil, Architectural, and Environmental Engineering, University of Texas at Austin , Austin, Texas 78712, United States.
authors: Bryant A
authors: BA
authors: Chambers
authors: A R M Nabiul
authors: AR
authors: Afrooz
authors: Sungwoo
authors: S
authors: Bae
authors: Nirupam
authors: N
authors: Aich
authors: Lynn
authors: L
authors: Katz
authors: Navid B
authors: NB
authors: Saleh
authors: Mary Jo
authors: MJ
authors: Kirisits
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000378:metabolism; D002712:Chlorides / Q000737:chemistry* / Q000494:pharmacology; D004777:Environment; D004926:Escherichia coli / Q000187:drug effects*; D007477:Ions / Q000494:pharmacology; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000633:toxicity / Q000648:ultrastructure; D009994:Osmolar Concentration; D018384:Oxidative Stress / Q000187:drug effects; D012834:Silver / Q000737:chemistry*; D012995:Solubility; D012996:Solutions / Q000494:pharmacology; D014867:Water / Q000737:chemistry
chemical_list: D000900:Anti-Bacterial Agents; D002712:Chlorides; D007477:Ions; D012996:Solutions; D014867:Water; D012834:Silver