ISSN 00124966, Doklady Biological Sciences, 2010, Vol. 431, pp. 124–127. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © S.A. Ostroumov, G.M. Kolesov, 2010, published in Doklady Akademii Nauk, 2010, Vol. 431, No. 4, pp. 566–569.
124
Study of biogenic migration of elements is an
important line of biosphere research [1–8]. Biogenic
migration of elements in aquatic ecosystems, both
freshwater and saltwater, is important for water self
purification and quality formation [9–11].
Data on element accumulation and binding by
aquatic organisms, including macrophytes, are impor
tant for analyzing the organisms’ important role in
biogenic migration of elements in aquatic ecosystems.
The concentrations of some elements were deter
mined earlier in different biogenic samples, including
hydrobionts and biogenic detrital substances [9, 10].
However, these data were based on a limited set of
organisms and elements. There are no published data
on either gold (Au) content in Ceratophyllum demer
sum L. or interaction between Au nanoparticles and
aquatic macrophytes.
The goal of this work was to study the immobiliza
tion of Au nanoparticles added to the water medium of
microcosms in the presence of macrophyte hydro
bionts C. demersum L.
MATERIALS AND METHODS
Experiments were carried out in freshwater micro
cosms. C. demersum L., a widely spread freshwater
plant, was used to form microcosms. Aquatic macro
phytes and settled tap water (STW) were added to the
microcosms. C. demersum plants were collected in a
pond located in the floodplain of the upper Moscow
River.
After microcosm formation (Table 1), they were
incubated under natural photoperiodicity conditions.
The water temperature was maintained at 17°C.
Nanosize particles (NSPs) of colloidal Au were
added to the microcosms.
Obtaining NSPs. Particles were obtained by redox
condensation in the water phase [12] using chloroau
ric acid (Fluka, Germany). 1% HAuCl4 was added to
deionized water of a highdegree purity; mixture was
brought to the boiling point and agitated, and sodium
citrate was added. Boiling was continued, and then the
mixture was cooled to room temperature. IgG and
bovine serum albumin (BSA, fraction V; Sigma,
United States) [12, 13] were used as stabilizing supple
ments. To obtain the IgG–NSP conjugate, the NSP
preparation was mixed with IgG solution, then BSA
was added; the particles were separated by centrifuga
tion [13]. IgG–NSP conjugates were resuspended in a
0.01 M potasium phosphate buffer solution, pH 7.0.
The particle size was 20 ± 5 nm. The NSP prepara
tion contained 3 × 10–4 M Au. Two types of macro
phyte incubation in medium containing NSP were
used.
In first variant (microcosms 1 and 2), nanoparticles
without the protein covering were added (without IgG
treatment). In the second variant (microcosms 3 and 4),
nanoparticles with protein covering were added; i.e.,
Au NSPs pretreated with rabbit immunoglobulin
(IgG, 150 kDa). The added volume was 2 ml. The
treatment scheme was as follows: three additions in
each microcosm at 24h intervals. Incubation was over
24 h after the last addition. The total amount of Au added
to microcosms 1, 2, 3, and 4 was about 3.6 × 10–6 M. Au
NSPs were not added to microcosms 5 and 6 (control).
The Aquatic Macrophyte Ceratophyllum demersum
Immobilizes Au Nanoparticles after Their Addition to Water
S. A. Ostroumova and G. M. Kolesovb
Presented by Academician M.A. Fedonkin July 31, 2009
Received February 11, 2009
DOI: 10.1134/S0012496610020158
a Faculty of Biology, M.V. Lomonosov Moscow State University,
Moscow, 119991 Russia
b Vernadsky Institute of Geochemistry and Analytical
Chemistry, Russian Academy of Sciences, ul.Kosygina 19,
Moscow, 119991 Russia
GENERAL
BIOLOGY
Table 1. Composition of microcosms containing C. demer
sum macrophytes in 500 ml of STW
System
component 1 2 3 4 5 6
C. demersum L.
(dry weight), g
7.1 5.8 5.0 5.6 5.7 5.1
Additives, NSP Au Au AuIgG AuIgG – –
Note: A dash means a control sample without Au.
DOKLADY BIOLOGICAL SCIENCES Vol. 431 2010
THE AQUATIC MACROPHYTE CERATOPHYLLUM DEMERSUM 125
After termination of all incubations, macrophytes
were removed from all the six microcosms, dried, and
triturated. Neutron activation analysis (NAA) was car
ried out. We used this method earlier to measure con
centration of elements in hydrobionts [11]; this
method was proved to be effective for analyzing ele
ment contents in samples of biological origin.
Sample preparing and detection of elements were
carried out as follows.
Specimens for analysis were dried at 105°С; then,
samples in the weight interval from 15 to 25 mg were
collected and packed together with samples for com
parison (KH, ST1, SGD1, FFA, RUS1, Allende,
BCR, etc.) and reference samples in aluminum foil
packages.
Samples were placed in an aluminum holder and
exposed to radiation from 15 to 20 h in the thermal
channel of the nuclear reactor of the Moscow Institute
of Engineering and Physics. After radiation treatment,
the samples were cooled, repacked in clean ampoules
to minimize the background. The activity was mea
sured two or three times (5–7 and 15–30 days after
irradiation) using semiconductor (highresolution)
germanium detectors (ORTEC) and NUC8192,
4096channels impulse analyzer (EMC, Hungary).
Spectrum identification and calculation of element
content was carried out in an automated mode as
described in [11].
The composition of STW used in microcosm for
mation was studied by inductively coupled plasma
atomic emission spectrometry (AES–ICP) using an
ICP spectrometer (ICAP9000, Thermo Jarrel Ash).
The water composition is shown in Table 2.
RESULTS AND DISCUSSION
The results of element determination using NAA
are shown in Table 3. It should be noted that the con
tents of some elements in the C. demersum phytomass
considerably varied. The content of the studied ele
ments in control samples of C. demersum phytomass
decreased (averaged data) in the following order: Zn >
Sr > Zr > Au > Sc. After incubation in the presence of
Au nanoparticles, the Au content became the highest,
and the order of elements changed to Au > Zn > Sr >
Zr > Sc. Only the Au content increased significantly in
C. demersum macrophytes from macrocosms 1–4
(Table 3). The contents of other elements (Sr, Sc, Zn,
and Zr) in C. demersum macrophytes from macro
cosms 1–4 did not differ substantially from that in the
control variants (5 and 6). These data are in good
agreement with the fact that these elements (in con
trast to Au) were absent in the additives to micro
cosms. Thus, the concentrations of these elements
served as additional control values.
The mean content of Au in the phytomass of
microcosms 3 and 4 did not differ from the Au content
in the phytomass of microcosms 1 and 2 (Table 3).
This means that Ig treatment had no effect on Au
immobilization in the studied macrophytes.
One can calculate the arithmetic mean Au accu
mulation values in microcosms 1–4 under the condi
tions of incubation of the plants in the presence of Au
nanoparticles. This value was 1204.95 ± 287.69 μg/g
dry weight (the standard deviation is indicated). The
mean content of Au in the C. demersum phytomass of
control microcosms (5 and 6) was 2.80 μg/g dry
weight. Thus, the Au content in C. demersum phyto
mass after incubation in the presence of Au nanopar
ticles exceeded the mean level in the control micro
cosms by a factor of 430.3.
At this stage, we were interested in measurement of
the total amount of Au associated with phytomass,
including both surfacebound Au and that potentially
penetrating into plant tissues. In future, we intend to
find out whether the penetration takes place. Our data
give no answer to this question. This study continues
our research in possibility of using macrophytes to
eliminate metals from the water medium with which
these plants contact [14]. An increase in the Au con
tent in phytomass proved that the plants absorbed this
element from the water medium, because there were
no other ways of Au intake.
Estimation of approximate accumulation of
immobilized elements by C. demersum phytomass on
Table 2. The element composition of water (aquatic medi
um) microcosms
Element Concentration (mg/l)
Al 0.06
B 0.01
Ba 0.03
Ca 49.4
Cd <0.001
Co <0.001
Cr <0.01
Cu <0.001
Fe 0.007
K 2.3
Li <0.01
Mg 12.6
Mn 0.016
Mo <0.01
Na 10.7
Ni <0.002
Pb <0.005
Si 5.1
Sr 0.14
Ti <0.001
Zn <0.001
126
DOKLADY BIOLOGICAL SCIENCES Vol. 431 2010
OSTROUMOV, KOLESOV
large areas of ecosystem bottom, where the phytomass
may reach 50 g, 500 g or 500 kg dry weight, can be
done on the basis of our data. Au accumulation could
reach 60.2 mg, 602.5 mg, and 602.48 g, respectively.
Our calculations are approximate. They are only
intended for estimation of the C. demersum phytomass
potential for Au accumulation, and it would be incor
rect to extrapolate the obtained results to natural eco
systems.
The characteristic feature of our study was that Au
immobilization occurred within a specific time by the
phytomass of a specific plant, with the studied element
added in the NSP form. Phytotoxicity of NSPs during
incubation of microcosms containing macrophytes
was not observed. However, we have no data to prove
definitely the absence of phytotoxicity of Au NSPs.
This study was the first to determine the concentra
tion of Au and some other elements in C. demersum
phytomass after incubation in microcosms containing
Au NSPs.
Thus, (1) the first data have been obtained that
demonstrate that a significant amount of Au NSPs
may bind to live phytomass of an aquatic plant,
C. demersum. As a result of binding and/or immobili
zation, the content of Au was greater then the back
ground level by a factor of 430.3; (2) modification of
NSPs with a protein (immunoglobulin) has no effect
on NSP immobilization by macrophytes.
The results contribute to understanding the role of
these organisms in biogenic migration of elements.
These data give us the possibility to estimate the par
ticipation of phytomass of the studied macrophyte
species in element concentration (as exemplified by
Au) in an aquatic system.
Vernadsky had placed special emphasis on “the
importance …of living masses … as places of the most
intense migration of atoms in the biosphere” and
highlighted the concentration function as one of the
main functions of living matter [1]. Our data on Au
immobilization by C. demersum phytomass confirm
these statements by a specific example. The new
results complete published data on the multifunctional
role of the biota in the migration of elements and cou
pling of geochemical and hydrobiological processes
[1–11]. Accumulation of new data on Au NSP inter
action with aquatic organisms is of interest for studies
on the interaction of Au and Au NSPs with cells and
organisms, which has medical implications, and for
the development of biotechnology of water purifica
tion and pathogen detection [15].
ACKNOWLEDGMENTS
We thank Yu.A. Moiseeva, E.A. Solomonova,
G.Yu. Kazakov, and A.V. Klepikova for assistance and
valuable comment.
Table 4. Detection of Au content in parts of ecosystems and biogenic samples
Sample Au content Reference
Biogenic detritus in microcosms where the following
hydrobionts were kept for a long time: Viviparus vivi
parus, Unio pictorum, Ceratophyllum demersum
from 0.025 to 0.27 (on average,
0.15) mg/kg detritus (dry weigh)
This study
Phytomass of C. demersum On average, 2.80 μg/g dry weigh The same
Phytomass of C. demersum after incubation with NSPs Increase by a factor of 430.3 The same
Shells of Unio pictorum On average, 0.06 μg/g According to [11]
Shells of Viviparus viviparus On average, 0.006 μg/g According to [11]
Marine sediments 1 × 10–8 gmol/kg On average, according to [7]
Iron and manganese nodules in the world ocean 1 × 10–8 gmol/kg On average, according to [7]
Table 3. Content of Au and other elements in C. demersum phytomass in experimental microcosms 1–6 (μg/g dry mass)
using NAA results
Element
Microcosm no. and presence of Au NSPs
1 (+Au) 2 (+Au) 3 (+AuIgG) 4 (+AuIgG) 5 (–Au) 6 (–Au)
Sr 43 36 79 32 30 25
Sc 0.02 0.03 0.04 0.049 0.023 0.034
Zn 780 620 880 1480 810 1710
Zr 30 27 25 26 20 32
Au 1040.6 1331.0 904.2 1544.0 5.54 0.057
DOKLADY BIOLOGICAL SCIENCES Vol. 431 2010
THE AQUATIC MACROPHYTE CERATOPHYLLUM DEMERSUM 127
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