Low-temperature ¹Н NМR spectroscopic study of hydration properties of a hybrid system based on nanosilica, DNA and doxorubicin in the presence of C₆₀ fullerene
The structure of hydrate cover layers of SiO₂–DNA–Dox (where Dox: doxorubicin) and SiO₂–DNA–Dox–C₆₀ fullerene hybrids was studied by means of low-temperature ¹H NMR spectroscopy in tetrachloromethane. The hydration properties of SiO₂–DNA–Dox nanomaterials combined with fullerenes and their derivativ...
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Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України
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irk-123456789-1194382017-06-07T03:05:26Z Low-temperature ¹Н NМR spectroscopic study of hydration properties of a hybrid system based on nanosilica, DNA and doxorubicin in the presence of C₆₀ fullerene Turov, V.V. Prylutskyy, Yu.I. Ugnivenko, A.P. Barvinchenko, V.N. Krupskaya, T.V. Tsierkezos, N.G. Ritter, U. Наноструктуры при низких температурах The structure of hydrate cover layers of SiO₂–DNA–Dox (where Dox: doxorubicin) and SiO₂–DNA–Dox–C₆₀ fullerene hybrids was studied by means of low-temperature ¹H NMR spectroscopy in tetrachloromethane. The hydration properties of SiO₂–DNA–Dox nanomaterials combined with fullerenes and their derivatives are extremely important for their further use as therapeutics in cancer treatment and for safety reasons. The findings reveal that the hydration properties of the hybrids differ from those of the solid DNA particulates or SiO₂–DNA systems due to the existence of different types of water clusters, namely the weakly- (WAW) and stronglyassociated water (SAW) clusters. For SAW clusters the radial distributions as well as the distributions of change in Gibbs free energy due to adsorptive interactions at the surfaces of the investigated systems were obtained. 2014 Article Low-temperature ¹Н NМR spectroscopic study of hydration properties of a hybrid system based on nanosilica, DNA and doxorubicin in the presence of C₆₀ fullerene / V.V. Turov, Yu.I. Prylutskyy, A.P. Ugnivenko, V.N. Barvinchenko, T.V. Krupskaya, N.G. Tsierkezos, U. Ritter // Физика низких температур. — 2014. — Т. 40, № 3. — С. 309-316. — Бібліогр.: 26 назв. — англ. 0132-6414 PACS 61.05.Qr, 61.46.–w, 82.56.Ub http://dspace.nbuv.gov.ua/handle/123456789/119438 en Физика низких температур Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України |
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Наноструктуры при низких температурах Наноструктуры при низких температурах |
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Наноструктуры при низких температурах Наноструктуры при низких температурах Turov, V.V. Prylutskyy, Yu.I. Ugnivenko, A.P. Barvinchenko, V.N. Krupskaya, T.V. Tsierkezos, N.G. Ritter, U. Low-temperature ¹Н NМR spectroscopic study of hydration properties of a hybrid system based on nanosilica, DNA and doxorubicin in the presence of C₆₀ fullerene Физика низких температур |
| description |
The structure of hydrate cover layers of SiO₂–DNA–Dox (where Dox: doxorubicin) and SiO₂–DNA–Dox–C₆₀ fullerene hybrids was studied by means of low-temperature ¹H NMR spectroscopy in tetrachloromethane. The hydration properties of SiO₂–DNA–Dox nanomaterials combined with fullerenes and their derivatives are extremely important for their further use as therapeutics in cancer treatment and for safety reasons. The findings reveal that the hydration properties of the hybrids differ from those of the solid DNA particulates or SiO₂–DNA systems due to the existence of different types of water clusters, namely the weakly- (WAW) and stronglyassociated water (SAW) clusters. For SAW clusters the radial distributions as well as the distributions of change in Gibbs free energy due to adsorptive interactions at the surfaces of the investigated systems were obtained. |
| format |
Article |
| author |
Turov, V.V. Prylutskyy, Yu.I. Ugnivenko, A.P. Barvinchenko, V.N. Krupskaya, T.V. Tsierkezos, N.G. Ritter, U. |
| author_facet |
Turov, V.V. Prylutskyy, Yu.I. Ugnivenko, A.P. Barvinchenko, V.N. Krupskaya, T.V. Tsierkezos, N.G. Ritter, U. |
| author_sort |
Turov, V.V. |
| title |
Low-temperature ¹Н NМR spectroscopic study of hydration properties of a hybrid system based on nanosilica, DNA and doxorubicin in the presence of C₆₀ fullerene |
| title_short |
Low-temperature ¹Н NМR spectroscopic study of hydration properties of a hybrid system based on nanosilica, DNA and doxorubicin in the presence of C₆₀ fullerene |
| title_full |
Low-temperature ¹Н NМR spectroscopic study of hydration properties of a hybrid system based on nanosilica, DNA and doxorubicin in the presence of C₆₀ fullerene |
| title_fullStr |
Low-temperature ¹Н NМR spectroscopic study of hydration properties of a hybrid system based on nanosilica, DNA and doxorubicin in the presence of C₆₀ fullerene |
| title_full_unstemmed |
Low-temperature ¹Н NМR spectroscopic study of hydration properties of a hybrid system based on nanosilica, DNA and doxorubicin in the presence of C₆₀ fullerene |
| title_sort |
low-temperature ¹н nмr spectroscopic study of hydration properties of a hybrid system based on nanosilica, dna and doxorubicin in the presence of c₆₀ fullerene |
| publisher |
Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України |
| publishDate |
2014 |
| topic_facet |
Наноструктуры при низких температурах |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/119438 |
| citation_txt |
Low-temperature ¹Н NМR spectroscopic study of hydration properties of a hybrid system based on nanosilica, DNA and doxorubicin in the presence of C₆₀ fullerene / V.V. Turov, Yu.I. Prylutskyy, A.P. Ugnivenko, V.N. Barvinchenko, T.V. Krupskaya, N.G. Tsierkezos, U. Ritter // Физика низких температур. — 2014. — Т. 40, № 3. — С. 309-316. — Бібліогр.: 26 назв. — англ. |
| series |
Физика низких температур |
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Low Temperature Physics/Fizika Nizkikh Temperatur, 2014, v. 40, No. 3, pp. 309–316
Low-temperature 1Н NМR spectroscopic study
of hydration properties of a hybrid system based
on nanosilica, DNA and doxorubicin in the presence
of C60 fullerene
V.V. Turov1, Yu.I. Prylutskyy2, A.P. Ugnivenko1, V.N. Barvinchenko1, T.V. Krupskaya1,
N.G. Tsierkezos3, and U. Ritter3
1O.O. Chuiko Institute of Surface Chemistry of NAS of Ukraine, 17 Gen. Naumov Str., Kyiv 03680, Ukraine
2Taras Shevchenko National University of Kyiv, 64 Volodymyrska Str., Kyiv 01601, Ukraine
E-mail: prylut@ukr.net
3Technical University of Ilmenau, 25 Weimarer Str., Ilmenau 98693, Germany
Received August 14, 2013, revised September 5, 2013
The structure of hydrate cover layers of SiO2–DNA–Dox (where Dox: doxorubicin) and SiO2–DNA–Dox–C60
fullerene hybrids was studied by means of low-temperature 1H NMR spectroscopy in tetrachloromethane. The
hydration properties of SiO2–DNA–Dox nanomaterials combined with fullerenes and their derivatives are ex-
tremely important for their further use as therapeutics in cancer treatment and for safety reasons. The findings
reveal that the hydration properties of the hybrids differ from those of the solid DNA particulates or SiO2–DNA
systems due to the existence of different types of water clusters, namely the weakly- (WAW) and strongly-
associated water (SAW) clusters. For SAW clusters the radial distributions as well as the distributions of change
in Gibbs free energy due to adsorptive interactions at the surfaces of the investigated systems were obtained.
PACS: 61.05.Qr Magnetic resonance techniques; Mössbauer spectroscopy (for structure determination only);
61.46.–w Structure of nanoscale materials;
82.56.Ub Structure determination with NMR.
Keywords: SiO2–DNA–Dox–C60 fullerene hybrid system, weakly- and strongly-associated water clusters, Gibbs
free energy, 1H NMR spectroscopy.
1. Introduction
Doxorubicin (further referred as Dox) is a complex hete-
rocyclic compound [1,2], poorly soluble in water and weak-
ly polar organic solvents that is able to form inclusion com-
pounds with the DNA molecules, and this determines the
mechanism of its action on cancer cells [3]. Transdermal
drug administering could be a promising way for treatment
of tumors. To create composite/hybrid systems capable of
effectively delivering medications through the skin, it is
necessary for these systems to contain special additives that
transform the interfacial water (intra- and extracellular) into
a distinct clustered state [4]. It is possible to accomplish this
by using mixtures of certain polar (e.g., DMSO) and non-
polar (e.g., aliphatic hydrocarbons) of organic compounds in
combination with particles of highly dispersed silica and
some types of biopolymer molecules (e.g., starch or DNA).
In this case, it may be necessary to employ corrective
nanoscale additives, such as water-soluble C60 fullerenes
[5,6]. One can achieve the reduction of the desorption rate of
Dox through noncovalent binding to DNA [7]. To investi-
gate the structure of interfacial water clusters by low-
temperature 1H NMR spectroscopy in complex heterogene-
ous systems in the presence of the organic medium one
should use aprotic solvents, such as CCl4, instead of weakly
polar (aliphatic) components.
We have previously shown that both the DNA and its
adsorption complexes with silica exhibit the ability to
structure hydrate water in a medium of weakly polar or-
ganic solvents in such a way that several signals of water
© V.V. Turov, Yu.I. Prylutskyy, A.P. Ugnivenko, V.N. Barvinchenko, T.V. Krupskaya, N.G. Tsierkezos, and U. Ritter, 2014
mailto:prylut@ukr.net
V.V. Turov, Yu.I. Prylutskyy, A.P. Ugnivenko, V.N. Barvinchenko, T.V. Krupskaya, N.G. Tsierkezos, and U. Ritter
are recorded in the 1H NMR spectra [7]. These signals
correspond to the formation at phase boundaries of clusters
with different average number of hydrogen bonds per each
water molecule. Additional control of the surface proper-
ties in nanosilica/DNA-based composite can be achieved
by introducing particles of nanocarbon material C60 fuller-
ene into the surface layer [8]. The surface of C60 fullerene
is formed by sp2 hybridized carbon atoms [9], providing
high lipophilicity and also the possibility for interaction
between the electrodonor functional groups and the π-sys-
tem of the C60 fullerene. Besides, the C60 fullerene alone
as well as in combination with Dox demonstrates high anti-
tumor activity [10–12], which may have a positive impact
on the properties of many fullerene-containing medicinal
compounds [13,14].
Thus, the aim of this work was to study the hydration
properties of the hybrid adsorbent based on a nanosilica
A-300, adsorptionally modified DNA and loaded with Dox
as well as influence of C60 fullerene nanoparticles on prop-
erties of this system outlined above.
2. Experimental
2.1. Material
Highly dispersed silica (HDS, Aerosil А-300, Kalush
Experimental Plant of the O.O. Chuiko Institute of Surface
Chemistry of NAS of Ukraine) with a specific surface of
300 m2/g was used as mineral component of the hybrid.
Highly stable water colloid C60 fullerene solution with
concentration 1 mg/ml was prepared by transfer of C60
molecules (purity > 99.5%) from toluene to water using
ultrasound sonication [6]. Theoretical calculations and ex-
perimental data (probe microscopy, dynamic light and
small-angle neutron scattering measurements) show that
the colloid solution of C60 fullerenes in water contain
mainly both individual C60 molecules (~0.7 nm diameter)
as well as their clusters (~2–100 nm diameter), in a hydrat-
ed state [10,11,15–19].
For the synthesis of the hybrid 0.2 g of DNA (Sigma,
Germany) and 0.0015 g of Dox (Pharmacia & Upjohn, Italy;
the structural formula of the Dox molecule is given
on Fig. 1) were dissolved in 90 ml of distilled water and
resulting solution was freeze-dried in vacuum. Afterwards,
a mixture of the obtained complex (0.06 g) with Aerosil
A-300 was mechanically activated in an agate mortar in the
presence of a small amount of water. After of approximately
30 min of activation a biopolymer loaded with Dox uniform-
ly covered the surface of the silica particles. This was ac-
companied by an increase in its bulk density from 50 up to
200 mg/g. Nanosilica presents in aqueous suspensions in the
form of aggregates of 20–50 nm radius. During the creating
SiO2–DNA–Dox composite by mechano-chemical activa-
tion method the new aggregates form, in which one or more
DNA molecules are surrounded by a nanoscale labile cap-
sule consisting of silica particles. The process of formation
of SiO2–DNA–Dox aggregates is controlled by the mini-
mum value of the free energy of the “silica–biopolymer”
system. It can be argued that the content of DNA in it corre-
sponds to 0.2–0.4 of statistical monolayer.
Placement of C60 molecule onto the surface of the hy-
brid particles of SiO2–DNA–Dox was carried out by wet-
ting them in a suspension of C60 fullerene in distilled water
(~1 g per 100 mg SiO2). This method provided an even
surface distribution of C60 fullerene and its relatively high
concentration in the hybrid (~0.8%) by weight relative to
the mass of the solid.
2.2. 1Н NMR spectroscopy
NMR spectra were recorded on a high-resolution NMR
spectrometer (Varian “Mercury”) with an operating fre-
quency of 400 MHz. 90 degrees 3 µs probe pulses were
employed. The temperature in the sensor was regulated by
a thermal control device Bruker VT-1000 with an accuracy
of ±1 degree. The signal intensities were determined by
fitting the spectra with multiple Gaussian peaks and then
measuring the peak areas. We performed zero line and
phase optimization with an accuracy, which for well-
resolved peaks was not worse than 5%, and for overlap-
ping peaks was ±10%. To prevent overcooling of water in
the objects of interest, the concentration of unfrozen water
was measured during heating of the samples pre-cooled to
210 K. The NMR measurement technique as well as the
thermodynamic properties and the radii of the clusters of
the interfacial water were described in detail in previous
published papers [20–22].
During the analysis of the interfacial phenomena, to
study the processes occurring at the solid–liquid–vapor
interface two main approaches are employed — the meth-
od of excess Gibbs quantities and the method of a layer of
finite thickness [23]. Within the former, it is assumed that
the excess energy due to the formation of phase boundaries
is concentrated in an infinitely thin surface layer, whereas
the rest of the thermodynamic parameters of the fluid do
Fig. 1. Structural formula of the Dox molecule.
310 Low Temperature Physics/Fizika Nizkikh Temperatur, 2014, v. 40, No. 3
Low-temperature 1Н NМR spectroscopic study of hydration properties of a hybrid system
not differ from those of the bulk. In order to determine the
geometric dimensions of the fluid volumes bounded by a
solid surface, the following Gibbs–Thomson equation can
be used that connects the relating radius (R) of the spheri-
cal or cylindrical water cluster with the magnitude of the
freezing point depression:
,
,
2
( ) sl m
m m m
f
T
T T R T
H R
∞
∞
σ
∆ = − =
∆ ρ
, (1)
where ( )mT R is the melting point of ice, localized in the
pores of radius R; Tm,∞ is the melting point of bulk ice; ρ is
the density of the solid phase; slσ is the energy of the so-
lid–liquid interaction and fH∆ is the bulk enthalpy of fu-
sion.
Equation (1) can be used to calculate the pore size dis-
tribution from the temperature dependence of the concen-
tration of unfrozen water Cuw(T). The latter is obtained by
employing the 1H NMR spectroscopy for layered water
freeze-out for aqueous suspensions of solids or hydrated
biological objects, when application of other methods for
analysis of porous structures is quite difficult [24]. In prac-
tice, Eq. (1) can be used in a modified form / ,mT k R∆ =
where ,2 /( )sl m fk T H∞= σ ∆ ρ is a constant for many hetero-
geneous water-containing systems with magnitude of about
50 [22,24].
In the method of a layer of finite thickness [23] it is as-
sumed that the effect of the interface extends over several
molecular layers deep into the liquid phase. Then the pro-
cess of freezing (or melting) of the interfacial water
trapped in the solid porous matrix is occurring in accord-
ance with the changes in Gibbs free energy (∆G), due to
the influence of the surface. This influence is decreasing
away from the surface of the interface. At T = 273 K water
freezes, with its properties similar to those of the bulk, and
with further decrease of temperature (excluding the effects
of over-freezing) freezing of water layers occurs very close
to the surface. At that temperature, the following relation
holds for the interfacial water
∆Gice = −0.036 (273.15 − Т), (2)
where the numerical coefficient is a parameter related to
the temperature coefficient of change in the Gibbs free
energy for ice. Amounts of strongly- (SAW) and weakly-
associated water (WAW), as well as the thermodynamic
properties of these layers, can be calculated in accordance
with the method described in detail in literature [20–22], in
which the Cuw(T) temperature dependence is determined
from the signal intensity.
As was shown previously [20–22], the method of the
low-temperature 1H NMR spectroscopy with a liquid
phase freeze-out allows calculating the amounts of associ-
ated water, its thermodynamic characteristics, and the size
distribution of water-filled nanoscale cavities in macro-
molecules. The magnitude of the chemical shift in hydro-
gen atoms (δH) in the associated water determines the ave-
rage number of H-bonds per water molecule. Since for the
non-associated water (gas phase, solution in a weakly polar
solvent) δH = 1–1.5 ppm, whereas for ice δH = 7 ppm
[22,25], it can be concluded that the participation of water in
the formation of one H-bond in H2O as a proton donor and
in another as an electron donor leads to an increase of δH by
2.7 ppm. Studies of various systems [20–22] have shown
that within a certain hydrophobic-hydrophilic balance of the
surface functional groups, water can transform into the WAW
state represented by the protons signal at δH = 1–2 ppm. In
this state, the average number of H-bonds per water mole-
cule does not exceed 1 (out of 4 possible), otherwise the H-
bond structure is strongly distorted compared to that of the
bulk water since the decrease in the O–H...O angle leads to
an increase in magnetic shielding of protons [26].
The measurements were performed in CCl4 organic sol-
vent medium. For the determination of the chemical shifts,
tetramethylsilane (TMS) was used as internal standard (the
concentration of TMS did not exceed 0.2 wt%).
3. Results and discussion
Figure 2 shows 1H NMR spectra of water in SiO2–DNA–
Dox hybrids containing different amounts of water. The 1H
NMR spectra were recorded at different temperatures
in CCl4. Concentration of water in the original sample
(Fig. 2(a)) was 5 mg/g. Varying the concentration was car-
ried out in two ways: either by adding water to the slurry
with a micro-dispenser (Fig. 2(b)) and its transfer to the
adsorbent through the CCl4 phase or by adding water to a
dry powdered substance and equilibration of the sample
through 10 min of vigorous shaking with a subsequent sus-
taining it in a vial for 1 h before adding CCl4 (Fig. 2(c)).
Dehydration of the initial sample was performed by heat-
ing it at 350 K for 10 min (Fig. 2(d)).
Figure 2 shows that water in the original hybrid sample
can be observed as three signals with chemical shifts of
0.5–1.3 ppm (WAW) and 4–5 ppm (SAW). With rising
temperature, there is an obvious shift of the signals toward
stronger magnetic fields (smaller values of δH), which may
be due to a decrease of association of water in clusters
[20]. In the spectra the signal of TMS, which is added to
CCl4 as a standard reference, can be also observed.
The freezing point of the dispersive medium (CCl4) is
about 230 K. As it can be seen in Fig. 2, the interfacial
water and TMS can be still observed in the spectra at lower
temperatures. Consequently, the nonpolar medium, even
after freezing, has little effect on the mobility of the TMS
and water molecules. It is likely that a fraction of the or-
ganic medium in contact with the nanoparticles remains in
unfrozen state, allowing water molecules that form the
cluster structures to maintain both the rotational and the
translational mobility. At the same time, the TMS molecules
can congregate in nanoscale cavities, in which increasing
concentrations of TMS lower the freezing point of CCl4.
Low Temperature Physics/Fizika Nizkikh Temperatur, 2014, v. 40, No. 3 311
V.V. Turov, Yu.I. Prylutskyy, A.P. Ugnivenko, V.N. Barvinchenko, T.V. Krupskaya, N.G. Tsierkezos, and U. Ritter
WAW can be observed in the 1H NMR spectra in two
signals (WAW1 and WAW2). Similar spectra were also
observed for WAW in both powdered solid DNA and
DNA immobilized on silica nanoparticles [7]. Peculiarity
of the system under study is in that both signals, WAW1
and WAW2, shift toward stronger magnetic fields with a
decrease in temperature, whereas for solid DNA a signifi-
cant shift into weaker magnetic fields was observed for the
WAW1 signal, the intensity of which remains lower over
the entire temperature range compared to that for the
WAW2 signal. Probably, the differences should be at-
tributed to the presence of Dox in the hybrid. The Dox
molecules reduce the likelihood for the interfacial water
molecules to participate in the formation of hydrogen-
bonded complexes with electron-donating centers in the
DNA molecules.
With the increase of water concentration
2H O( )C up to
105 mg/g (Fig. 2(c)) there is a significant rise in the SAW
signal intensity with a relatively weak change in the rela-
tive intensities of the WAW1, WAW2 and TMS signals.
Thus, the amount of WAW depends primarily on the struc-
tural characteristics of the composite surface and changes
rather insignificantly with the variation of 2H O.C
With an addition of more water into the a sample through
the organic solvent phase (Fig. 2(b)), the spectra change
significantly compared to those shown in Fig. 3(a),(c) and
SAW freezing occurs at a relatively higher temperature. At
~273 K two SAW signals are recorded in the spectra having
different values of the chemical shift, with δH = 3–4 ppm
for the main SAW signal indicating a significant decrease
in the strength of association. The SAW signal vanishes for
low magnetic fields at T < 270 K, therefore it is subject to
fairly large water aggregates [24]. Most likely those are
SAW microdroplets located near the phase boundaries of
the composite particles. Due to its high viscosity, the col-
loidal system can remain in a non-equilibrium state for
long time, however, the surface affinity of the composite
particles to water remains high, as evidenced by the find-
ings presented in Fig. 2. Thus, according to the findings
shown in Fig. 2, the amount of water that can be adminis-
tered into the hydrate shell of the composite can be in-
creased six-fold.
Figure 2(d) shows 1H NMR spectra obtained at differ-
ent temperatures for a sample dehydrated by keeping it at
T = 350 K. In these spectra there is practically no SAW
signal, whereas the WAW signal intensity decreased by less
than a factor of 2. Therefore, it can be concluded that all the
WAW is strongly bound and its removal from the surface
occurs at significantly greater energy loss than for SAW.
1H NMR spectra obtained at different temperatures for
the SiO2–DNA–Dox–C60 fullerene hybrid samples are
shown in Fig. 3. The weight concentration of C60 mole-
Fig. 2. 1H NMR spectra of water in SiO2–DNA–Dox hybrid recorded at different temperatures, various concentrations of interfacial
water, as well as different processes of water addition.
312 Low Temperature Physics/Fizika Nizkikh Temperatur, 2014, v. 40, No. 3
Low-temperature 1Н NМR spectroscopic study of hydration properties of a hybrid system
cules in the composite was adjusted in order to be compa-
rable to that of DNA. For the same sample the measure-
ments were performed in air (Fig. 3(a)) and in CCl4 ambi-
ent (Fig. 3(b)). Then additional amount of water has been
introduced into the sample through the organic solvent
phase (Fig. 3(c)).
From the comparison of the spectra shown in Fig. 3(a)
and 3(b) it can be seen that the presence of weakly polar
forms of water is largely determined by the presence of the
weakly-polar organic solvent phase. Although in the origi-
nal sample (Fig. 3(a)) there is a certain asymmetry of the
signal (especially at ~273 K), which may be associated
with the presence of a small amount of WAW, it is too
weak to reveal itself as an isolated signal. The chemical
shift of the SAW signal in air ambient changes from 5 ppm
at 200 K to 4 ppm at 280 K due to the somehow weaker
tendency of association of water with increasing tempera-
ture. The intensity of the water signal changes insignifi-
cantly demonstrating the strong binding of water to the
surface of solid particles of the dispersed phase.
In the CCl4 ambient the spectra change dramatically
(Fig. 3(b)). At 280 K the SAW and WAW signals are ob-
served in the spectra with similar intensities. The SAW
signal has a chemical shift in the range of 3.2–4 ppm, i.e.,
the association of SAW is significantly lower than for the
same sample in air. Another feature is the freezing of SAW
at relatively high temperature (above 240 K). Thereby,
according to published results [22] it should be classified
as weakly bonded water. Introduction of additional amount
of water into the colloidal system (Fig. 3(c)) leads to an
increase in intensity of the SAW signal. Moreover, its inten-
sity becomes less sensitive to temperature variations. Com-
parison of the spectra shown in Fig. 2(a) and 3(a) suggests
that the transition of water into the WAW state is due pri-
marily to the presence of the C60 fullerene nanoparticles.
Similarly to what was observed for the SiO2–DNA–Dox
hybrid (Fig. 2(b)) with the introduction of an additional
amount of water through the nonpolar CCl4 medium, SAW
can be detected in the spectra shown in Fig. 3. This SAW,
which has not penetrated into the adsorption layer of the
composite particles, is present in the form of fairly large
clusters or nanodomains. Such nonequilibrium aqua-aggre-
gates can exist long enough (at least for several hours).
Probably, they are stabilized by the confinement-related
limitations for the diffusion of water within the inter-
particle space of the hybrid filled with CCl4 toward the
hydrophilic regions of the surface.
Figure 4 shows the temperature changes of SAW and
WAW signal intensity at various water concentrations in
the SiO2–DNA–Dox and SiO2–DNA–Dox–C60 fullerene
hybrids. Figure 5 presents the distributions, calculated ac-
cording to Eq. (1) and (2), of: (a) the sizes of adsorbed
water clusters and (b) their energy of interaction with the
phase boundaries. Since the measurements were performed
in the temperature range of 200–280 K, for the fraction of
water that remained in the unfrozen state it was provision-
ally assumed that it exists in the form of clusters with an
average radius of 0.4 nm.
For SiO2–DNA–Dox the CSAW(T) dependence (Fig. 4(a))
seems to be sensitive not only to the 2H OC magnitude, but
also to the method of introduction of additional portions of
water. Thus, when 2H OC = 15 mg/g for T < 240 K, the
CSAW (T) curve lies below that one for a sample containing
less water. This finding indicates a significant change in
the size of water clusters and their energy of interaction
with the interface. Indeed, from Fig. 5, it can be seen that
when 2H OC = 5 mg/g, water is in the form of clusters
smaller than 5.1 nm, whereas when 2H OC = 15 mg/g the
Fig. 3. 1H NMR spectra of water in SiO2–DNA–Dox–C60 full-
erene hybrid recorded at different temperatures in air (a), CCl4
ambient with
2H OC = 5 mg/g (b), and CCl4 ambient with
2H OC = 32.6 mg/g (c).
Low Temperature Physics/Fizika Nizkikh Temperatur, 2014, v. 40, No. 3 313
V.V. Turov, Yu.I. Prylutskyy, A.P. Ugnivenko, V.N. Barvinchenko, T.V. Krupskaya, N.G. Tsierkezos, and U. Ritter
range of cluster sizes is 0.8–5.5 nm. Hence, the decrease in
the Gibbs free energy due to the adsorption interactions for
the initial sample
2H O(C = 5 mg/g) is the greatest and
reaches –3.5 kJ/mol, while for the sample in which the
water content is increased by introduction through the or-
ganic phase 2H O(C = 15 mg/g), the decrease in the Gibbs
free energy does not exceed –2.25 kJ/mol (Fig. 5(b)).
When balancing the sample with an additional portion of
water in air 2H O(C = 105 mg/g) one can observe in the
dCSAW (R) and dCSAW (∆G) distributions, water clusters the
sizes of which vary across the entire measurable range,
while the ΔG magnitude can exceed –3.5 kJ/mol (such
water freezes at T < 200 K).
For the SiO2–DNA–Dox–C60 fullerene hybrid the
CSAW (T) dependence at constant 2H OC changes substan-
tially when air ambient is replaced with CCl4 (Fig. 4(b)).
For T < 240 K, the slope increases significantly due to eas-
ing of water solidification under the influence of nonpolar
Fig. 4. Temperature dependences for the concentration of SAW
(a), (b) and WAW (c) for the SiO2–DNA–Dox and SiO2–DNA–
Dox–C60 fullerene hybrids.
5 mg/g H O 2 in CCl4
15 mg/g H O 2 in CCl4
105 mg/g H O 2 in CCl4
100
10
1
C
SA
W
, m
g/
g
200 220 240 260 280
T, K
200 220 240 260 280
T, K
2.6 mg/g H O 2 in CCl4
32.6 mg/g H O 2 in CCl4
2.6 mg/g H O 2 on air
0.8% C60
200 220 240 260 280
T, K
10
1
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
C
W
AW
, m
g/
g
C
SA
W
, m
g/
g
2.6 mg/g H O, C2 60
32.6 mg/g H O, C2 60
5 mg/g H O2
15 mg/g H O2
105 mg/g H O2
(b)
(c)
(a)
Fig. 5. Cluster radius distribution (a) and distribution of the
changes (b) in the Gibbs free energy due to adsorption interac-
tions for clusters of adsorbed water.
20
10
0
1 10
4
2
0
1 10
101
1 10
101
1 10R, nm
2
1
0
1
0
0
5
10
2
0
dC
SA
W
, m
g/
g
dC
SA
W
, m
g/
g
C60, 2.6 mg/g H O on air2
C in CCl60 4, 32.6 mg/g H O 2
5 mg/g H O2 in CCl4
15 mg/g H O2 in CCl4
105 mg/g H O in CCl2 4
dC
SA
W
, m
g/
g
C in CCl60 4, 2.6 mg/g H O 2
(a)
–3.5 –3.0 –2.5 –2.0 –1.5 –1.0 –0.5 0
20
10
0
–3.5 –3.0 –2.5 –2.0 –1.5 –1.0 –0.5 0
–3.5 –3.0 –2.5 –2.0 –1.5 –1.0 –0.5 0
–3.5 –3.0 –2.5 –2.0 –1.5 –1.0 –0.5 0
–3.5 –3.0 –2.5 –2.0 –1.5 –1.0 –0.5 0
–3.5 –3.0 –2.5 –2.0 –1.5 –1.0 –0.5 0
0
1.0
2
2.0
4
0
0
4
8
1.0
0.5
0
0
2
1
(b)
dC
SA
W
, m
g/
g
dC
SA
W
, m
g/
g
dC
SA
W
, m
g/
g
314 Low Temperature Physics/Fizika Nizkikh Temperatur, 2014, v. 40, No. 3
Low-temperature 1Н NМR spectroscopic study of hydration properties of a hybrid system
organic medium. As a result, the average radius of water
clusters increases from 0.4 to 0.8 nm (Fig. 5(a)), while a
lowering of the Gibbs free energy from –3.5 to –2.25 kJ/mol
(Fig. 5(b)) occurs.
Similar effect was previously observed for many types
of carbon materials and certain types of mesoporous silica
[21,22]. It occurs because during the formation of SAW
clusters on a weakly hydrophilic surface they interact with
the surface by forming a relatively small number of hydro-
gen bonds. At the same time, they interact, as a whole sys-
tem, with the surface via dispersion interactions. In the
case of shared adsorption of water and excess nonpolar
substance at the surface the effectiveness of dispersion
interactions with the organic phase is higher than with wa-
ter. As a result, CCl4 penetrates into the narrow gap be-
tween the clusters and the SAW surface, reducing in this
way the binding energy of the SAW clusters due to in-
creasing distance from the surface. According to Fig. 4(b),
the average size of water clusters increases in the presence
of CCl4. It is accompanied by a simultaneous decrease in
the number of small SAW clusters.
For both hybrid materials (SiO2–DNA–Dox and
SiO2–DNA–Dox–C60), WAW can be described as tightly
bound because it freezes at T < 250 K [21]. The only excep-
tion is the SiO2–DNA–Dox sample with water added through
the CCl4 phase (Fig. 4(c)). One can assume that WAW is
stabilized by the organic environment and exists in the form
of small clusters, in which water molecules interact with each
other mainly via the dipole–dipole mechanism. Furthermore,
such structures are formed with the participation of not only
the active surface centers, but also the CCl4 molecules.
According to Eq. (1), the WAW cluster size should not
exceed 1.2 nm, but however in the present study a reliable
determination of the structure of these clusters was not able
to be done.
4. Conclusions
Properties of interfacial water in a hybrid created by an
adsorptive attachment of DNA–Dox at the surface of A-300
silica differ significantly from the hydration properties of
the SiO2–DNA system. In CCl4 medium, 1H NMR SAW
signals are measured at the surface as well as two types of
WAW signals. However, no signal is observed for water
associated with electron-donor centers of DNA molecules,
which are otherwise detected in solid powdered DNA. This
probably occurs due to a significant change in the structure
of interfacial water clusters resulting in accelerated molec-
ular exchange between different types of adsorbed water.
Inclusion of C60 fullerene nanoparticles into the SiO2–
DNA–Dox hybrid in CCl4 ambient reduces interaction of
SAW clusters with the surface, due to certain distance be-
tween the clusters and the surface, as well as due to the
change in the cluster size distribution (trending toward for-
mation of larger water clusters). It is, thus, possible to con-
trol the hydration properties of the Dox-loaded SiO2–DNA
hybrid, and, in particular, the abundance and size ratio of
the WAW/SAW clusters.
It was found that the addition of water into the colloidal
system based on the SiO2–DNA–Dox and SiO2–DNA–
Dox–C60 fullerene hybrids and CCl4 leads to the formation
in them of long-lived nonequilibrium submicron size water
clusters, which are weakly bound to the surface of the par-
ticles and affect significantly their hydration properties.
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