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Research Article
Preparation of Silica Nanoparticles Loaded with Nootropics and
Their In Vivo Permeation through Blood-Brain Barrier
Josef Jampilek,1Kamil Zaruba,2Michal Oravec,3Martin Kunes,1Petr Babula,1
Pavel Ulbrich,4Ingrid Brezaniova,2Radka Opatrilova,1Jan Triska,3and Pavel Suchy1
1Faculty of Pharmacy, University of Veterinary and Pharmaceutical Sciences Brno, Palackeho 1/3, 612 42 Brno, Czech Republic
2Faculty of Chemical Engineering, University of Chemistry and Technology Prague, Technicka 5, 166 28 Prague 6, Czech Republic
3Global Change Research Centre AS CR, Belidla 986/4a, 603 00 Brno, Czech Republic
4Faculty of Food and Biochemical Technology, University of Chemistry and Technology Prague, Technicka 5,
16628Prague6,CzechRepublic
Correspondence should be addressed to Josef Jampilek; josef.jampilek@gmail.com
Received September ; Revised January ; Accepted February
Academic Editor: Narasimha Murthy
Copyright © Josef Jampilek et al. is is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
e blood-brain barrier prevents the passage of many drugs that target the central nervous system. is paper presents the
preparation and characterization of silica-based nanocarriers loaded with piracetam, pentoxifylline, and pyridoxine (drugs from
the class of nootropics), which are designed to enhance the permeation of the drugs from the circulatory system through the blood-
brain barrier. eir permeation was compared with non-nanoparticle drug substances (bulk materials) by means of an in vivo model
of rat brain perfusion. e size and morphology of the nanoparticles were characterized by transmission electron microscopy. e
content of the drug substances in silica-based nanocarriers was analysed by elemental analysis and UV spectrometry. Microscopic
analysis of visualized silica nanocarriers in the perfused brain tissue was performed. e concentration of the drug substances in the
tissue was determined by means of UHPLC-DAD/HRMS LTQ Orbitrap XL. It was found that the drug substances in silica-based
nanocarriers permeated through the blood brain barrier to the brain tissue, whereas bulk materials were not detected in the brain.
1. Introduction
Nootropics are a wide and structurally heterogeneous class
of drugs (also supplements, nutraceuticals, and functional
foods) that improve one or more aspects of mental func-
tion, such as working memory, motivation, and attention.
ey can be also referred to as smart drugs, memory
enhancers, neuroenhancers, cognitive enhancers, and intelli-
gence enhancers. eir therapeutic eect is based on positive
aection of metabolic pathways in brain tissue (improved
utilization of nutrients and mediators) and their impact
manifests aer some time of administration. ey are used
especially at insult of brain by a trauma, ischemia, intoxica-
tion, and hypoxia as well as at neurodegenerative disorders
such as Alzheimer’s disease, Parkinson’s disease, Hunting-
ton’s disease, and attention decit hyperactivity disorder
(ADHD).Anumberofnootropicsaresyntheticanaloguesof
physiological compounds (such as acetylcholine, pyridoxine,
GABA, or coenzyme Q10); others are natural compounds
(e.g., vinpocetine); and the rest are other cerebral-active
compounds (e.g., nimodipine, pentoxifylline, etc.) [,].
e site of action of all these drugs is brain; that is,
they must overcome all barriers to achieve the brain tissue,
and the blood-brain barrier (BBB) is the last, critical, and
serious obstacle for the permeation of drugs that require CNS
action. e BBB represents a structure with complex cellular
organisation that separates the brain parenchyma from the
systemic circulation. It consists of brain capillaries that
support endothelial cells and are surrounded by astrocytic
end-foot processes. e BBB also acts as a metabolic barrier
due to the presence of numerous enzymes. ese enzymes can
either metabolise potentially harmful drugs to CNS-inactive
compounds or convert inactive drugs to their active CNS
metabolites or degrade them into metabolites or substrates of
Hindawi Publishing Corporation
BioMed Research International
Volume 2015, Article ID 812673, 9 pages
http://dx.doi.org/10.1155/2015/812673
BioMed Research International
N
O
O
N
N
N
N
O
O
O
N
OH
HO
HO
Piracetam Pentoxifylline Pyridoxine
CH3
CH3
CH3
NH2
H3C
F : Structures of investigated drugs.
specic eux transporters, such as P-glycoprotein/multidrug
resistance proteins [–].
All the above mentioned properties of the barrier result
in strong selection of permeating drugs depending on
their physicochemical properties, such as molecular weight,
molecular volume, lipophilicity, ionisation state, and/or their
anity to specic transporters (uptake/eux transporters)
[,]. e cellular organisation of the BBB and the presence of
transmembrane proteins enable a selective regulation of the
passage of molecules from the blood to the brain. Molecules
present in the blood stream can reach the CNS by two
dierent pathways, the paracellular pathway (through tight
junctions) and the transcellular pathway (through endothe-
lial cells). Molecules that reach the CNS via the transcellular
pathway can diuse passively, be actively transported by
specic transporters, or undergo endocytosis [,]. To
circumvent the BBB and allow an active CNS compound to
reach its target, many strategies exist. ey can be sorted with
respect to the BBB as either invasive (direct injection into
the cerebrospinal uid or therapeutic opening of the BBB) or
noninvasive such as use of alternative routes of administra-
tion (e.g., nose-to-brain route and olfactory and trigeminal
pathways to brain), inhibition of eux transporters, chemical
modication of drugs (prodrugs and bioprecursors), and
encapsulation of drugs into nanocarriers (e.g., liposomes,
polymeric nanoparticles, and solid lipid nanoparticles) [,].
Nanoparticles as drug carriers have also been extensively
studied recently. eir uptake into the brain is hypothesised
to occur via adsorptive transcytosis and receptor-mediated
endocytosis [,]. Particle size, surface anity, and stability
in circulation are important factors inuencing the brain
distribution of colloidal particles [,].
Silica-based nanoparticles are widely used in nanotech-
nology in the biomedical sector, because they are easy to
prepare and inexpensive to produce. eir specic surface
characteristics, porosity, and capacity for functionalization
make them good tools for biomolecule detection and sep-
aration, providing solid media for drug delivery systems
and for contrast agent protectors. In addition, they are used
as safe and biocompatible pharmaceutical additives [–].
Incorporation of a drug into nanocarriers may change the
drug bioavailability, physicochemistry, and pharmacokinet-
ics, which can be advantageous in many applications [,].
As mentioned above, silica-based nanoparticles are well-
known to be biocompatible easy-to-prepare nontoxic carriers
thatareabletotransportloadeddrugsinlivingorganisms
[–]. What is not so well-known (only a few papers have
been published so far), they are also able to penetrate through
BBB which is used for transport of silica nanoparticles []
and silica-coated nanoparticles []. e aim of this study
was the preparation of these silica-based nanocarriers loaded
with piracetam, pentoxifylline, and pyridoxine (see Figure )
and investigation of their permeation through the BBB in
comparison with bulk drug substances to enhance absorption
and concentration of these cerebral-active drugs in brain.
2. Experimental and Methods
2.1. General. All reagents were purchased from Sigma-
Aldrich, Life Technologies, or Fisher Chemical and were of
analytical grade. Acetonitrile hypergrade for LC-MS LiChro-
solvR was supplied by Merck KGaA (Darmstadt, Germany).
Methanol hypergrade for LC-MS LiChrosolvR was supplied
by Merck KGaA (Darmstadt, Germany). Acetic acid was
obtained from Sigma-Aldrich Chemie GmbH (Steinheim,
Germany). e Purelab Classic (ELGA LabWater, High
Wycombe, Bucks, UK) was used to generate high purity water
for preparation of aqueous mobile phase.
2.2. Preparation of Nanoparticles. e silica nanoparticles
were made via a modied Stober method [–]. e typical
reaction solution consisted of methanol (.%, mL),
ammonium hydroxide (% wt of ammonia, mL), and
drug solution ( mg/mL for piracetam, – mg/mL for
others, mL). On mixing the solution by vigorous magnetic
stirring, tetraethylorthosilicate (TEOS) (.%, . mL) was
added dropwise to initiate the hydrolysis reaction. e
resulting solution was stirred at room temperature for h.
e particle suspension was repeatedly ( times) collected by
centrifugation ( min, , G) and washed with methanol
to ensure the removal of all unreacted reactants. Finally, the
nanoparticles were dried to yield a nal product of drug-
loaded silica nanocarriers.
2.3. Elemental Analysis and UV Spectrometry. e content
of API (. mg/ mg nanoparticles) in silica nanoparticles
was determined by elemental analysis and UV absorption.
Elemental analysis was performed using a Vario EL III
Universal CHNOS Elemental Analyzer (Elementar Anal-
ysensysteme, Germany) and loading was calculated from
the corresponding increase of nitrogen content when drug-
loaded nanoparticles were analysed in comparison with non-
loaded nanoparticles. Calculated loadings for pentoxifylline
and pyridoxine were in accordance with those estimated by
UV absorption by determination of unbound drug removed
by nanoparticle washing. e corresponding verication
BioMed Research International
200 nm
(a)
200 nm
(b)
200 nm
(c)
200 nm
(d)
F : TEM microphotographs of pure silica nanoparticle (a), silica-based nanocarriers loaded with piracetam (b), pentoxifylline (c), and
pyridoxine (d).
of piracetam loading estimated by elemental analysis was
not possible due to piracetam absorption below nm.
Absorption measurements were performed using a Cintra
spectrometer (GBC Scientic Equipment, USA).
2.4. Transmission Electron Microscopy. e particle size and
the morphology of the samples were examined by trans-
mission electron microscopy (TEM). Samples for TEM were
prepared by putting a drop of the colloidal dispersion in
methanol ( 𝜇L) on a copper grid covered with thin amor-
phous carbon lm. Samples were dried before inserting them
in the specimen holder of a transmission electron microscope
JEOL JEM- and observed at kV. Pictures were taken
by a digital camera SIS Megaview III (So Imaging Systems)
and analysed by AnalySIS . soware. e average particle
size was calculated from at least particles. e results are
illustrated in Figures and .
2.5. Rat Brain Perfusion. Male Wistar rats (– g) pur-
chased from the breeding facility Anlab (Prague, Czech
Republic)wereusedinthestudy.Animalsweremaintained
under standard conditions of temperature and lighting and
givenfoodandwaterad libitum. For surgical preparation,
rats were anesthetized intramuscularly with ketamine and
xylazine.einsituratbrainperfusiontechniquewasused
with modications according to the previously described
methods [–]. External jugular veins were prepared and
cannulated for freely blood owing out of the veins. At the
same time, carotid arteries (on the le and right sides) were
0
20
40
60
80
100
120
140
160
180
200
Si
Si-piracetam
Si-pentoxifylline
Si-pyridoxine
Particle size (nm)
121 ± 38 nm
120 ± 54 nm
112 ± 45 nm
128 ± 53 nm
F : Particle size [nm] of individual nanoparticles: pure silica
nanoparticles, Si-piracetam, Si-pentoxifylline, and Si-pyridoxine.
Particle size is expressed as mean diameter ±∗SD (𝑛>50
particles).
prepared and cannulated using intravascular catheter lled
with heparinized saline ( U/mL) for perfusion. Ligation
was accomplished caudally to the catheter implantation site.
e catheter in the carotid artery was connected to a syringe
lled with buered Krebs-Henseleit saline solution con-
taining NaCl (. g/L), NaHCO3(. g/L), KCl (. g/L),
NaH2PO4⋅H2O (. g/L), CaCl2(. g/L), MgCl2⋅H2O
BioMed Research International
50𝜇m
(a)
50𝜇m
(b)
50𝜇m
(c)
50𝜇m
(d)
F : Microscopic photographs of histological preparations of control rat brain tissue (a) and rat brain tissues treated with Si-piracetam
(b), Si-pentoxifylline (c), and Si-pyridoxine (d) as stained with PDMPO (green uorescence) in combination with Hoechst (nuclei,
blue uorescence).
(. g/L), and -glucose . g/L, as also used in previous
perfusion studies [,]. Polyvinylpyrrolidone ( g/L) was
added into the perfusate to maintain physiological oncotic
pressure in the perfusion medium. e perfusion uid was
ltered, warmed to ∘C, and gassed with % O2and %
CO2. Immediately prior to the perfusion the pH and osmo-
larity of this solution were . and mOsm, respectively.
e perfusion uid was infused into the carotid artery with
an infusion pump for s at ow rate . mL/min. is
perfusion rate was selected to maintain the carotid artery
pressure of mmHg []. e rectal temperature of the
animal was maintained at 37 ± 0.5∘C throughout the surgery
by a heat pad connected to a feedback device. At the end
of perfusion, rats were decapitated and the whole brain was
removed from the skull. Cerebral hemispheres were dissected
and stored to next analysis aer removal of the arachnoid
membrane and meningeal vessels (deeply frozen at −∘Cfor
HPLC analysis and tissues for histological examination were
xed in % formaldehyde).
2.6. Microscopic Analysis of Brain Tissue: Visualization of
Silicates. e deposition of silicates in brain tissue was visual-
ized using 𝑁-[-(dimethylamino)ethyl]--{-[-(pyridin--
yl)-,-oxazol--yl]phenoxy}acetamide(PDMPO).emod-
ied procedure described by Shimizu et al. was used [].
Briey, sections were deparanised and rehydrated (xylene,
mixture xylene/ethanol : , ethanol, % ethanol, %
ethanol, % ethanol, Na-phosphate buer (. M, pH .)).
en the sections were incubated in 𝜇MsolutionofPDMPO
in . M Na-phosphate buer (pH .) for hours at ∘C
(laboratory temperature). Aer incubation, the sections were
costained with a Hoechst uorescent probe (Sigma-
Aldrich, USA) to visualize nuclei washed three times with
PBS buer and observed with a microscope using an appro-
priate excitation lter (Axioscop , Zeiss, Germany). Typical
photographs are shown in Figure .
2.7. Analysis of Brain Tissue. Samples of brain tissue aer
perfusion with bulk materials (non-nanoparticle drug sub-
stances) and drug-loaded silica nanocarriers were frozen
and homogenized before extraction. Solid-liquid extraction
in methanol was used as an ecient method. Extracts
were subsequently puried, concentrated, and analysed. e
samples of brain tissue (without purication) perfused with
piracetam were also analysed by direct injection (overdosing
loop) on UHPLC-HRMS. Direct injection was used for the
samples where the concentration of the drug was close to
or lower than the limit of detection or quantication. Direct
injection was not useful for more samples because it can
contaminate UHPLC-HRMS.
Isolated drugs from brain tissue and from silica nanopar-
ticles were analysed by a UHPLC-HRMS separation sys-
tem (Dionex UltiMate Liquid Chromatography Sys-
tems) equipped with diode array detection (DAD) and a
hybrid high resolution mass spectrometer LTQ Orbitrap XL
(ermoFisher Scientic, USA/Dionex RSLC, Dionex, USA).
BioMed Research International
A chromatographic column Hypersil Gold (ermo Scien-
tic, USA), C 𝜇m, . × mm, was used. e mixture
of MeCN-HPLC grade (.%) and H2O-HPLC grade with
.% AcOH (.%) was used as a mobile phase. e total
ow of the column was . mL/min, column temperature was
∘C, and the time of analysis was min.
e records were evaluated from the DAD and HRMS-
Orbitrap. e wavelengths of nm, nm, nm,
nm, and – nm were monitored. MS and MSnwere
performed using the HRMS LTQ Orbitrap XL (ermoFisher
Scientic, USA) equipped with a HESI II (heated electrospray
ionization)source.Orbitrapwasoperatedinfullscanwith
resolution ,. Full scan spectra were acquired over mass
range 𝑚/𝑧 – in the positive mode. Orbitrap was
also operated in SIM (select ion monitoring): . (as a
qualier ion) and . (as a qualier ion without NH2
group) under Δppm for piracetam; . under Δppm
for pentoxifylline; and . (as a qualier ion) and
. (as qualier ion without OH group) under Δppm
for pyridoxine. e resolution and sensitivity of Orbitrap
were controlled by injection of the standard (piracetam,
pentoxifylline, and pyridoxine) aer analysing of every
samples, and the resolution was also checked by the help of
lock masses (phthalates). Blanks were also analysed within
the sequence aer analysis of each sample. e compounds
were checked in the mass library that was created from
measurement of standards of piracetam and pentoxifylline
andpyridoxineintheMSandMS
nmodes of Orbitrap.
3. Results and Discussion
e content of drug substances in silica-based nanocarriers
was analysed by elemental analysis and conrmed by UV
absorption analysis of supernatants (except of piracetam).
Loading eciency was tested by the addition of an increasing
concentration (, , and mg/mL) of drug solution to the
reaction mixture for nanoparticle preparation. For both com-
pounds (pentoxifylline and pyridoxine) the loading eciency
was about % for concentration of drug stock solution and
mg/mL. When mg/mL drug stock solution was added,
the amount of the drug loaded was below the detection
limit of the used method. Approximately the same loading
eciency (i.e., %) was conrmed for all three drugs
by elemental analysis. Only nanoparticles with the highest
loading (i.e., those prepared using a drug stock solution of
mg/mL) were subjected to the animal study. It was found
that.mgofdrugsubstanceisinmgofnanoparticles
with batch to batch variance less than %. e particle size
and the shape of prepared silica nanocarriers with loaded
piracetam, pentoxifylline, and pyridoxine (Si-piracetam, Si-
pentoxifylline, and Si-pyridoxine) were measured by TEM
(see Figure ). A control sample of pure silica nanoparticles
was prepared and characterised. It was found that the average
particle size of all prepared nanoparticles was approximately
nm (TEM microphotographs of pure silica nanoparticles
and nanocarriers with loaded drugs in Figure are shown
with 5x magnication). It is evident that the general shape
of all particles can be considered as spherical. Based on %
condence interval computed from the mean diameter plus
or minus twice the standard deviations (see Figure ), it can
be stated that no statistical signicance was found for the
samples.
Microscopic photographs of histological preparations
(samples of brain tissue aer perfusion with bulk drug
solution and Si-drugs) are shown in Figure .Incomparison
with control rat brain tissue (Figure (a)), signicant changes
in uorescence in silica-based nanocarriers were recorded
for piracetam (Figure (b)), pentoxifylline (Figure (c)), and
pyridoxine (Figure (d)). In these photographs, both nuclei
and cytoplasmic structures have been identied as PDMPO-
positive (green uorescence). No PDMPO uoresce has been
identied in control, untreated samples. In addition, also
tissue treated with bulk material alone was investigated.
In this case, no changes in uorescence (not shown) were
observed. PDMPO (Lysosensor DND- Yellow/Blue) was
originally developed to visualize acidic compartments in the
cells []. On the other hand, it has been established that
it has unique properties allowing to evaluate the deposition
of silica in cells and tissues. PDMPO-Si complex possesses
unique uorescent properties in the presence of silicic acid,
producing bright green uorescence aer UV excitation.
PDMPO has successfully been established to visualize silica
in diatoms and other organisms. For example, Znachor et al.
used PDMPO to study the deposition of silica in Fragilaria
crotonensis Kitton []. is compound was also studied
for the distribution and deposition of silicates in horsetail,
Equisetum arvense L. Shimizu et al. showed on the silica gel
that PDMPO is able to label silicates directly []. In the light
of this fact, it was decided to use it as a probe to visualize
deposition of silica-based nanoparticles in tissues.
e samples of brain tissue aer perfusion with bulk
materials (drugs solutions) and drug-loaded silica nanocar-
riers were analysed by direct injection (over dosing loop)
on UHPLC-HRMS. Also extracted drug substances from the
samples of the perfused tissues were analysed. While the
bulk drug substances were extracted from perfused brain
tissues easily practically by any of the applied methods, the
extraction of the nanonized drug substances from the tissues
or from silica nanocarriers was problematic. Dierent extrac-
tion techniques for isolation of the drugs from the tissue and
the nanocarriers were tested, such as classical liquid extrac-
tion (LE), sequent extraction by various solvents (methanol,
water, acetonitrile, etc.), solid-liquid extraction, accelerated
solvent extraction (ASE), and ultrasound extraction (USE).
e individual extraction methods were compared. e used
methods showed similar eectivity; nevertheless the solid-
liquid extraction in methanol with minimum losses of the
studied compounds was selected.
For example, the brain tissue samples with piracetam and
Si-piracetam were compared. Concentrations of piracetam
in brain tissues measured by the UHPLC-HRMS using indi-
vidual extraction methods were comparable (– ng/mL,
– ng/g brain tissue). For Si-piracetam concentrations
measured by individual extraction methods were also com-
parable ( pg/mL– ng/mL, pg/g brain tissue–. ng/g
brain tissues) but with lower extraction eciency. e extrac-
tion eciency was especially inuenced by sorption of the
drug substances in silica-based nanocarriers. e determined
BioMed Research International
(a)
(b)
F : Comparison of concentration of bulk piracetam (a) and Si-piracetam (b) in brain tissue samples: this chromatogram presents very
low concentration of drug, close to limit of quantication (S/N close /). Found ratio of piracetam/Si-piracetam is approximately : .
concentrations in the samples of bulk piracetam were higher
than in the brain tissue samples with nanoparticles; see Figure
. e fact of the strong sorption of piracetam in silica
nanocarriers was conrmed using direct injection of the
brain tissue with the nanoparticles into the dosing loop and
subsequent multiple rinsing by solvent (methanol) and anal-
ysis by LC-MS (as mentioned below). Processing of extracts
(ltration and centrifugation) caused high losses; never-
theless the highest losses were observed at purication of
the extracts (–%), because nanocarriers were adsorbed
in the lters and on the vial wall. erefore, silica-based
nanoparticles were destroyed by borate buer (pH = .),
but at following LC-MS analysis various borate adducts and
dimers were determined; that is, the method does not seem
to be suitable.
As a solution of the above mentioned problems (sorption,
dimers, etc.), the samples were analysed by direct injection to
a sampling loop with subsequent multiple elution by MeOH.
e concentration of Si-piracetam determined by direct
injection was by several orders of magnitude higher com-
pared with the concentrations determined in the extracts.
By repeated injection of pure methanol the nanocarriers
were gradually disintegrated and Si-piracetam was released,
as illustrated in chromatograms in Figure . Concentrations
BioMed Research International
(a)
(b)
F : Chromatograms aer rst (a) and second (b) injections of pure methanol to sample of brain tissue with piracetam-loaded silica
nanocarriers(labelledsamplesasblank-puresolventinjectedintosampleofbrainwithnanoparticles.).
determined at the rst injection of pure solvent was –
ng/mL (– ng/mL in mg brain tissue), at the
second injection – ng/mL (– ng/mL in mg
brain tissue), which was by - orders of magnitude higher
than those measured during the extraction of brain tissue
with nanoparticles.
Basedonthissemiquantitativemethodofdirectinjection,
the concentrations of Si-piracetam that permeated through
theBBBtothebraincanbedeterminedincomparisonwith
drugs in bulk material; see Table . e concentration of
the permeated bulk piracetam in the brain tissue was .–
. ng/mL in mg brain tissue, while that of Si-piracetam
was–ng/mLinmgbraintissue;thatis,the
application of nanoparticles led to an increase of piracetam
approximately -fold. Similar strong sorption in silica
nanocarriers can be found for pentoxifylline and pyridoxine;
nevertheless, as mentioned in Section ., the direct injection
of the pentoxifylline samples was not performed due to the
contamination of UHPLC-HRMS system. However, based
on the results obtained for piracetam, it can be supposed
that the concentration of Si-pentoxifylline in the brain tissue
would be much higher, approximately – ng/mL
in mg of brain tissue. Although the silica nanocarriers
loaded with pyridoxine were detected by microscopic analysis
BioMed Research International
T : Concentrations of drug-loaded silica nanocarriers permeated through the BBB to brain in comparison with drugs in bulk (n.d. =
not detected).
Drug substance Concentration [ng/mL] in mg of brain tissue
Bulk Extraction of nanocarriers Direct injection of tissue with nanoparticles
Piracetam .–. .–. –
Pentoxifylline – .–. –∗
Pyridoxine n.d n.d —
∗Predicted based on the ratio bulk/direct injection of piracetam.
of brain tissue, no pyridoxine was found by UHPLC-HRMS;
see Table .
Itcanbestatedthatloadingofdrugstosilicananocarriers
and extraction of drugs from nanocarriers is governed by
general principles of normal-phase adsorption chromatogra-
phy; it means that the retention of a molecule (the strength of
interactions between the molecule and silica surface/silanol
groups) is determined by its polar functional groups/double
bonds and steric factors. Silica gel has acidic properties,
and, therefore, basic compounds interact with the surface of
this gel strongly []. us the observed strong binding of
the discussed drug substances in silica nanocarriers may be
caused by the presence of free electron pairs in the com-
pounds (basicity). e basicity of pyridoxine expressed as the
strongest p𝐾a(base) was 5.0±0.1(predicted by ACD/Percepta
ver. ), while for pentoxifylline the strongest p𝐾a(base)
was 0.5 ± 0.7 (ACD/Percepta ver. ) and for piracetam
the strongest p𝐾a(base) was −0.6 ± 0.2 (ACD/Percepta ver.
).Basedonthesedata,pyridoxineshowsthestrongest
potential bonding power, which may be a reason why it was
not extracted in a detectable amount.
4. Conclusions
e silica-based nanocarriers loaded with piracetam, pentox-
ifylline, and pyridoxine were prepared. e content of the
drug substances in silica-based nanocarriers was determined
by elemental analysis and spectrophotometry as . mg of
drug in mg of nanoparticles. By transmission electron
microscopy it was found that the average particle size of
all prepared nanoparticles was approximately nm, and
they had spherical shape. e permeation of the prepared
nanoparticles was compared with bulk materials by means of
the in vivo model of rat brain perfusion. Samples of rat brain
tissues were analysed by microscope, and it was found that
allsilica-basednanoparticlespermeatedtothebraintissue.
e concentration of the drug substances in the tissue was
determined by LC-HRMS. It was found that all the drugs
exhibited very strong sorption in silica nanocarriers. e
direct injection of samples of brain tissue (without purica-
tion) treated with Si-piracetam to a sampling loop with sub-
sequent multiple elution by MeOH conrmed approximately
-fold higher concentration of piracetam loaded in silica-
based nanocarriers in the brain tissue in comparison with
bulk piracetam.
e eld of nanomedicine proposes many opportunities
of nding novel solutions to improve health care. is study
conrmed that silica nanoparticles can permeate through the
blood-brain barrier and eectively transport drugs to the
brainandsohelpinthetreatmentofdierentdicultto
treat cerebral diseases. However, further investigation and,
primarily, selection of suitable drug candidates (bulky and
nonbasic) for immobilization into silica nanoparticle drug
formulations are needed.
Conflict of Interests
e authors declare that there is no conict of interests
regarding the publication of this paper.
Acknowledgments
isstudywassupportedbytheCzechScienceFoundation,
GACR P//, by the EfCOP, IPo Project ENVIMET
(CZ../../.) and by the National Infrastruc-
ture CzeCos/ICOS (LM). Ingrid Brezaniova received
fund no. A FCHI .
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