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Impacts of Select Organic Ligands on the Colloidal Stability, Dissolution Dynamics, and Toxicity of Silver Nanoparticles
journal contribution
posted on 2013-11-19, 00:00 authored by Lok R. Pokhrel, Brajesh Dubey, Phillip R. ScheuermanKey
understanding of potential transformations that may occur on
silver nanoparticle (AgNP) surface upon interaction with naturally
ubiquitous organic ligands (e.g., −SH (thoil), humic acid,
or −COO (carboxylate)) is limited. Herein we investigated how
dissolved organic carbon (DOC), −SH (in cysteine, a well-known
Ag+ chelating agent), and −COO (in trolox, a well-known
antioxidant) could alter the colloidal stability, dissolution rate,
and toxicity of citrate-functionalized AgNPs (citrate–AgNPs)
against a keystone crustacean Daphnia magna. Cysteine,
DOC, or trolox amendment of citrate–AgNPs differentially modified
particle size, surface properties (charge, plasmonic spectra), and
ion release dynamics, thereby attenuating (with cysteine or trolox)
or promoting (with DOC) AgNP toxicity. Except with DOC amendment,
the combined toxicity of AgNPs and released Ag under cysteine or trolox
amendment was lower than of AgNO3 alone. The results of
this study show that citrate–AgNP toxicity can be associated
with oxidative stress, ion release, and the organism biology. Our
evidence suggests that specific organic ligands available in the receiving
waters can differentially surface modify AgNPs and alter their environmental
persistence (changing dissolution dynamics) and subsequently the toxicity;
hence, we caveat to generalize that surface modified nanoparticles
upon environmental release may not be toxic to receptor organisms.