The appearance of renal cells cytoplasmic degeneration and nuclear destruction might be an indication of GNPs toxicity.

Abstract

Advances in nanotechnology have identified promising candidates for many biological and biomedical applications. Since the properties of nanoparticles (NPs) differ from that of their bulk materials, they are being increasingly exploited for medical uses and other industrial applications. The histological and the histochemical alterations in the renal tissues due to gold nanoparticles (GNPs) have not well documented and have not yet been identified. The aim of the present study was to investigate the particle-size effect of GNPs on the renal tissue in an attempt to address their potential toxicity.
A total of 70 healthy male Wistar-Kyoto rats were exposed to GNPs received 50 or 100 μl of GNPs infusion of size (10, 20 and 50 nm for 3 or 7 days) to investigate particle-size effect of GNPs on the renal tissue. Animals were randomly divided into groups, 6 GNPs-treated rats groups and one control group. Groups 1, 2 and 3 received infusion of 50 μl GNPs of size 10 nm (3 or 7 days), size 20 nm (3 or 7 days) and 50 nm (3 or 7 days), respectively; while groups 4, 5 and 6 received infusion of 100 μl GNPs of size 10 nm, size 20 nm and 50 nm, respectively.
The histological alterations were mainly seen in the cortex and the proximal renal convoluted tubules were more affected than the distal ones. In comparison with respective control rats, exposure to GNPs doses has produced the following renal tubular alterations: cloudy swelling and renal tubular necrosis. Interstitial alterations included: intertubular blood capillaries dilatation, intertubular hemorrhage and inflammatory cell infiltrations. The glomeruli showed moderate congestion with no hypercelluraity and mesangial proliferation or basement membrane thickening.
The induced histological alterations might be an indication of injured renal tubules due to GNPs toxicity that become unable to deal with the accumulated residues resulting from metabolic and structural disturbances caused by these NPs. These alterations were size-dependent with smaller ones induced more effects and related with time exposure of GNPs. The produced histological alterations may suggest that GNPs interact with proteins and enzymes of the renal tissue interfering with the antioxidant defense mechanism and leading to reactive oxygen species (ROS) generation which in turn may induce stress in the renal cells to undergo atrophy and necrosis. More histomorphologcal investigations are needed to address the potential threat of GNPs as a therapeutic and diagnostic tool.

Full text

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RESEARCHOpen Access
The appearance of renal cells cytoplasmic
degeneration and nuclear destruction might be
an indication of GNPs toxicity
Mohamed Anwar K Abdelhalim1*and Bashir M Jarrar2
Abstract
Background: Advances in nanotechnology have identified promising candidates for many biological and
biomedical applications. Since the properties of nanoparticles (NPs) differ from that of their bulk materials, they are
being increasingly exploited for medical uses and other industrial applications. The histological and the
histochemical alterations in the renal tissues due to gold nanoparticles (GNPs) have not well documented and
have not yet been identified. The aim of the present study was to investigate the particle-size effect of GNPs on
the renal tissue in an attempt to address their potential toxicity.
Methods: A total of 70 healthy male Wistar-Kyoto rats were exposed to GNPs received 50 or 100 μl of GNPs
infusion of size (10, 20 and 50 nm for 3 or 7 days) to investigate particle-size effect of GNPs on the renal tissue.
Animals were randomly divided into groups, 6 GNPs-treated rats groups and one control group. Groups 1, 2 and 3
received infusion of 50 μl GNPs of size 10 nm (3 or 7 days), size 20 nm (3 or 7 days) and 50 nm (3 or 7 days),
respectively; while groups 4, 5 and 6 received infusion of 100 μl GNPs of size 10 nm, size 20 nm and 50 nm,
respectively.
Results: The histological alterations were mainly seen in the cortex and the proximal renal convoluted tubules
were more affected than the distal ones. In comparison with respective control rats, exposure to GNPs doses has
produced the following renal tubular alterations: cloudy swelling and renal tubular necrosis. Interstitial alterations
included: intertubular blood capillaries dilatation, intertubular hemorrhage and inflammatory cell infiltrations. The
glomeruli showed moderate congestion with no hypercelluraity and mesangial proliferation or basement
membrane thickening.
Conclusions: The induced histological alterations might be an indication of injured renal tubules due to GNPs
toxicity that become unable to deal with the accumulated residues resulting from metabolic and structural
disturbances caused by these NPs. These alterations were size-dependent with smaller ones induced more effects
and related with time exposure of GNPs. The produced histological alterations may suggest that GNPs interact with
proteins and enzymes of the renal tissue interfering with the antioxidant defense mechanism and leading to
reactive oxygen species (ROS) generation which in turn may induce stress in the renal cells to undergo atrophy
and necrosis. More histomorphologcal investigations are needed to address the potential threat of GNPs as a
therapeutic and diagnostic tool.
Keywords: gold nanoparticles, renal tissue, histology, hydropic degeneration, nanotoxicity
* Correspondence: abdelhalimmak@yahoo.com
1Department of Physics and Astronomy, College of Science, King Saud,
University, P.O. Box 2455, Riyadh-11451, Saudi Arabia
Full list of author information is available at the end of the article
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http://www.lipidworld.com/content/10/1/147
© 2011 Abdelhalim and Jarrar; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.

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Introduction
Nanoparticles are an intermediate state of matter some-
where between bulk and molecular level. These particles
have important application for cell labeling and imaging,
drug delivery, biological sensors, diagnostic and thera-
peutic purposes mainly in cancer and photodynamic
therapy [1-6]. Studies revealed that the NPs were rapidly
taken into the system with the highest accumulation in
the liver, spleen, lungs, aorta, esophagus and olfactory
bulb [7]. Moreover, particles of nano-dimension are
believed to be more biologically reactive than their bulk
counter parts due to their small size and larger surface
area to volume ratio [7,8].
Gold in its bulk form has long been considered an
inert, noble metal with some therapeutic and even med-
icinal value hence GNPs are thought also to be relatively
non-cytotoxic [9]. Yet there are differing reports of the
extent of the toxic nature of these particles owing to
their different modifications, surface functional attach-
ments, shape and size [10,11]. Moreover, the metallic
nature of the metal derived NPs and the presence of
transition metals encourages the production of reactive
oxygen species (ROS) leading to oxidative stress [12,13].
Although some scientists consider NPs as nontoxic,
there are other studies reporting the toxic effects of NPs
[14-16]. While some NPs may appear to be nontoxic,
other cellular mechanisms such as cell signaling and
other normal cellular functions may be disrupted and
are currently undergoing further investigation [17,18].
The toxicity of NPs is being addressed by a number of
standardized approaches with in vitro, in vivo as well as
detailed genomic or biodistribution studies [18]. In addi-
tion, it has been shown that NPs may produce in vitro
toxicity in some cell-based assays, but not in others.
This may be a result of interference with the chemical
probes, differences in the innate response of particular
cell types, or other factors, a point to be considered
when GNPs are used as carriers for the delivery of
drugs and in gene therapy [19,20].
While nanotoxicity research is now gaining attention,
little is paid to the effect of size and period of NPs
mainly to their distribution and alterations in the tissue
[21,22]. In the present study, an attempt has been made
to address the possible histological alterations in the
renal tissues following exposure to GNPs and, if so,
whether the potential nanotoxicity is related to the size
of these particles and the time of exposure.
Materials and methods
A total of 70 healthy male Wistar-Kyoto rats obtained
from the Laboratory Animal Center (College of Phar-
macy, King Saud University, Saudi Arabia). The rats
nearly of the same age (12 weeks old) and weighing
220-240 gm of King Saud University colony were used.
Animals were randomly divided into groups, 6 GNPs-
treated rats groups and one control group. Following a
period of stabilization (7 days), 10, 20 and 50 nm
GNPs were administered intraperitonealy at the rate
for 3 or 7 days as follows: Group 1: received infusion
of 50 μl GNPs of size 10 nm for 3 or 7 days (n = 10);
Group 2: received infusion of 50 μl GNPs of size 20
nm for 3 or 7 days (n = 10); Group 3: received infu-
sion of 50 μl GNPs of size 50 nm for 3 or 7 days (n =
10); Group 4: received infusion of 100 μl GNPs of size
10 nm for 3 or 7 days; (n = 10); Group 5: received
infusion of 100 μl GNPs of size 20 nm for 3 or 7 days
(n = 10); Group 6: received infusion of 100 μl GNPs of
size 50 nm for 3 or 7 days; (n = 10); Control group:
received no GNPs (n = 10).
The rats were maintained on standard laboratory
rodent diet pellets and were housed in humidity and
temperature-controlled ventilated cages on a 12 h day/
night cycle. All experiments were conducted in accor-
dance with the guidelines approved by King Saud Uni-
versity Local Animal Care and Use Committee.
Fresh portions of both kidneys from each rat were cut
rapidly, fixed in neutral buffered formalin (10%), then
dehydrated, with grades of ethanol (70, 80, 90, 95 and
100%). Dehydration was then followed by clearing the
samples in 2 changes of xylene. Samples were then
impregnated with 2 changes of molten paraffin wax,
then embedded and blocked out. Paraffin sections (4-5
um) were stained with hematoxylin and eosin (the con-
ventional histological stain) according to Pearse [23].
Stained sections of control and treated rats were exam-
ined for alterations in renal tissue.
Results and discussions
No mortality occurred in any of the experimental
groups of the present investigation, and no alterations
were observed in the appearance and behavior of GNPs
treated rats in comparison with the control ones. In
comparison with the control group, the following histo-
logical alterations were detected in the renal tissue of
GNPs treated rats: The following tubular alterations due
to GNPs intoxication appeared in the renal tissue of the
treated rats.
GNPs produced occasional glomerular congestion in
the rats exposed to 10 nm or 20 nm particles for 7 days
but not in the glomeruli of the rats exposed to 50 nm
(Figure 1). Hypercellularity and mesangial proliferation
or glomerular basement membrane thickening was not
detected in the glomeruli of all GNPs treated rats. Occa-
sional dilatation of glomerular tuft blood capillaries was
observed. These little alteration showed by the glomeruli
might be due to the glomerular basement membrane
which forms a barrier that prevents nanoparticles accu-
mulation. Terentyuk et al., 2009 [24] have reported
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proliferation of epithelial cells of Bowman’s capsule by
GNPs where 15 nm particles showed more effect than
larger ones.
Dissociation of renal cells
dissociation of renal cells mainly next to glomerular
congested glomeruli was seen (Figure 1). This alteration
might indicate that GNPs affect renal cells adhesion and
induces cell-cell junction disruption. According to Inu-
maru et al., 2009 [25] oxidative stress is a crucial factor
to induce cell-cell dissociation.
Renal tubules necrosis
cellular necrosis was observed in the renal proximal
tubules of GNPs-treated rats. The degenerative tubules
showed swelling cytolysis and thinning or absence of the
proximal tubular brush border and tubular irregularity
(Figures 2 and 3). This alteration was more prominent
in the cortex than the medulla and was accompanied
with inter-tubular blood capillaries congestion and
accompanied cytoplasmic eosinophilia in some of the
necrotic proximal convoluted tubules. Tubular necrosis
was detected in the renal tubules of rats exposed to 20
nm size particles and to lesser extent with 10 nm ones
but was not seen with those exposed to 50 nm size par-
ticles. Necrosis was more prominent in the kidneys of
the rats received 100 μl than 50 μl and less in 3 days
than ones exposed to 7 days. Necrosis might be followed
by organelles swelling specially mitochondria, endoplas-
mic reticulum and rupture of lysosomes before shrink-
ing and dissolution of renal cells nuclei [26].
Inflammatory cells infiltration
Inflammatory cells infiltration was seen in renal tissue of
some GNPs treated rats. The infiltrate cells were mainly
neutrophils and mononuclear cells (Figure 4). This infil-
tration was more after 7 days of administration and in
rats received 100 μl than those received 50 μl but less
prominent in the kidneys of rats exposed to 50 nm par-
ticles. The appearance of inflammatory cells in the renal
tissue may suggest that GNPs could interact with pro-
teins and enzymes of the renal interstitial tissue interfer-
ing with the antioxidant defense mechanism and leading
to reactive oxygen species (ROS) generation which in
turn may imitate an inflammatory response [27]. Yen et
al., 2009 [28] have reported an induction of more
immunological responses with smaller GNPs than the
larger ones.
Interstitial alterations
The kidney of the GNPs treated rats showed the follow-
ing interstitial alterations: 1) Intertubular blood
Figure 1 Light micrographs of sections in the kidney of: GNPs-
treated rat received 100 μl of 10 nm particles for 3 days
demonstrating dissociation of renal cells next to glomerular
congested glomerulus.
Figure 2 Light micrographs of sections in the kidney of: GNPs-
treated rat received 50 μl of 20 nm particles for 3 days
demonstrating renal tubules necrosis.
Figure 3 Light micrographs of sections in the kidney of: GNPs-
treated rat received 100 μl of 10 nm particles for 7 days
demonstrating renal tubules necrosis.
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capillaries dilatation: the kidneys of GNPs treated rats
showed occasional inter-tubular blood capillaries dila-
tion in rats received 100 μl of 10 or 20 nm particles for
7 days (Figure 5). This dilatation might be due to the
decrease in the vascular resistance of the renal tissue
induced by GNPs; 2) Intertubular hemorrahage: Focal
intertubular hemorrhage was seen in the kidneys of rats
exposed to 100 μl of 10 or 20 nm particles for 7 days
(Figure 6).
The loop of Henle showed very little or no alterations
due to GNPs intoxication while occasional cytomegaly
and luminal hyaline casts were the only alterations
observed in the collecting tubules. The renal tissue of
the rats received 50 or 100 μl of 50 nm GNPs for 3 or 7
days showed little or no alterations while none of the
above alterations were observed in the renal tissue of
any member of the control group (Figures 7 and 8).
Studies indicated that distribution in the inner organs is
size dependent [24].
The results of the present work showed that the cor-
tex is more affected than medulla due to treatment with
GNPs. This could be partly due to uneven distribution
of these particles in the tissue of the kidney where
about 90% of the total renal blood flow enters the cortex
via the bloodstream. Accordingly, a relative high con-
centration of particles might reach the cortex via the
bloodstream than that would enter the medulla.
The findings of the present study indicate that the
potential toxicity of GNPs is dependent upon the size of
these particles. These findings are in line with the
reports of Pan et al., 2007 [29] where cell lines where
smallest GNPs demonstrated greatest toxicity compared
to larger ones. Similar conclusion has been reported by
Jong and Borm [30] when GNPs were injected
Figure 4 Light micrographs of sections in the kidney of: GNPs-
treated rat received 100 μl of 20 nm particles for 7 days
demonstrating inflammatory cell infiltration.
Figure 5 Light micrographs of sections in the kidney of: GNPs-
treated rat received 100 μl of 10 nm particles for 7 days
demonstrating intertubular blood capillaries dilatation.
Figure 6 Light micrographs of sections in the kidney of: GNPs-
treated rat received 100 μl of 20 nm particles for 7 days
demonstrating intertubular hemorrahage.
Figure 7 Light micrographs of sections in the kidney of: GNPs-
treated rat received 50 μl of 50 nm particles for 3 days
demonstrating normal glomerular structe.
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intravenously into mice. This might be due to the fact
that as size of a particle decreases, its surface area to
volume ratio increases, resulting in increased surface
reactivity with a tendency for toxicity even if the mate-
rial is relatively inert in a bulk form [31-33]. Also, sev-
eral studies indicate that the distribution of GNPs in the
body tissue is size dependent [34,35].
Conclusions
Histological alterations by GNPs exposure as shown in
the results of the present work could be an indication of
injured renal tissue due to GNPs toxicity that become
unable to deal with the accumulated residues resulting
from metabolic and structural disturbances caused by
these particles. One might conclude that these altera-
tions are size-dependent with smaller ones induced
more damage to renal tissue with relation with the time
exposure of GNPs. This might be due to earlier accu-
mulation of the larger NPs in the tissue while the smal-
ler ones stay much longer in the bloodstream due to
recirculation.
The appearance of renal cells cytoplasmic degenera-
tion and nuclear destruction may suggest that GNPs
interact with proteins and enzymes of the renal tissue,
interfering with the antioxidant defense mechanism and
leading to generation and accumulation of the reactive
oxygen species (ROS) which in turn may produce
inflammatory response and mitochondrial destruction
inducing stress in the renal cells to undergo atrophy,
necrosis and programmed cell death.
More histomorphologcal, histochemical and ultrastru-
cural investigations are needed to correlate the biomedi-
cal application of GNPs with their therapeutic and
diagnostic use in correlation with the size, chemical
composition, surface charge, solubility and surface struc-
ture of these particles.
Acknowledgements
The authors are very grateful to National Plan of Science and Technology
(NPST). This research was financially supported by the National Science and
Technology Innovation Plan (NSTIP), Research No. 08-ADV206-02 and
Research No. 09-NAN670-02, College of Science, King Saud University,
Saudi Arabia.
Author details
1Department of Physics and Astronomy, College of Science, King Saud,
University, P.O. Box 2455, Riyadh-11451, Saudi Arabia.2College of Applied
Medical Sciences, Al-Jouf University, Saudi Arabia.
Authors’ contributions
MAKA and BMJ have analyzed data, interpreted and written the final draft of
this manuscript. The animal model used in this study was obtained from the
Laboratory Animal Center (College of Pharmacy, King Saud University, Saudi
Arabia). Dr. MAKA has conceived the study and its design and obtained
research grants for this study. Moreover, both authors have read and
approved the final manuscript.
Competing interests
The authors declare that they have no competing interests.
Received: 14 July 2011 Accepted: 22 August 2011
Published: 22 August 2011
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Figure 8 Light micrographs of sections in the kidney of: GNPs-
treated rat received 100 μl of 50nm particles for 7 days
demonstrating normal renal tubules.
Abdelhalim and Jarrar Lipids in Health and Disease 2011, 10:147
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