Environmental Engineering Reference
In-Depth Information
Farkasetal.(
2010
)studiedthetoxiceffectsofsilverandgoldNPs(HAuCl
4
and
AgNO
3
)andtheirbulkcounterpartsonrainbowtrouthepatocytes(Table
7
). Silver
and gold NPs showed agglomeration in media of higher ionic strength and in the
presenceofdissolvedorganiccarbon(DOC).TheAgNPscausedcytotoxicityand
membrane disruption through ROS generation. However, gold NPs did not show
cytotoxicity,evenatathreefoldconcentration.Inasimilarstudy,Farkasetal.(
2011
)
evaluated effects on primary gill cells of rainbow trout (
Oncorhynchus mykiss
).
They assessed the cytotoxicity of citrate and PVP-coated AgNPs to primary gill
cellsofrainbowtroutatvaryingconcentrations(0.1-10mg/L)byusingmembrane
integrity and oxidative stress measurements. Compared to the PVP-coated AgNPs,
the citrate capped AgNPs were more easily absorbed into cells, resulting in increased
expression levels of glutathione.
6
Possible Mechanisms by Which Nanoparticles
Induce Toxicity
Nanoparticles are toxic to living organisms more because of their aggregation
behaviorthantheirsolubility.Inaddition,theshapeandsizeofNPsalsoaffecttheir
interactions with the cell surface and cytosolic components. NP-induced toxicity is
mainly mediated through the generation of ROS in cells.
6.1
Generation of ROS
DifferentENPsmayhavedifferentmechanismsofgeneratingROS.Size,shapeand
physico-chemical properties of the ENPs can influence the mechanism of ROS gen-
eration. Three exogenous ROS generation mechanisms have been postulated for
the ENPs:
1) Interaction of ENPs with water, oxygen or H
2
O
2
in the reaction medium. This
interaction facilitates the generation of oxygen free radicals and HO
.
radical in
presence of sunlight due to surface oxidation:
X + O
2
ₒ X
+
+ O
2
−.
h
+
+ OH ₒ HO
.
(Observedinthepresenceofsunlight),
Where, X is ENP and h
+
is electron holes.
2) Activation of inflammatory cells, like macrophages and neutrophils that can
phagocytose ENPs and generate ROS.
3) Cleavage of C-H bonds through a multistep reaction, followed by oxidative
damageofmacromoleculeslikelipidsandnucleicacids(Fenoglioetal.
2009
).
ENPscangenerateROSincellularcomponents(membranes,proteins,lipidsand
DNA) in several ways that include: intrinsic sources, such as mitochondrial respiratory
Search WWH ::
Custom Search