Download incorporation of anti-cancer drug on mesoporous silica

INCORPORATION OF ANTI-CANCER DRUG ON MESOPOROUS SILICA
NANOPARTICLES AND SYSTEM CHARACTERIZATION
S. P. Pereira*(1); A. R. H. Carollo(1); G. R. de Castro(2); R. M. Silveira(1); M. A. U.
Martines(1); J. Corsino(1); F. R. Garcez(1).
(1)
Universidade Federal de Mato Grosso do Sul – UFMS, CCET - Centro de Ciências
Exatas e Tecnologia – Pós-Graduação em Química –UNIDADE XI. Av. Filinto Müller,
1555, Vila Ipiranga, Caixa Postal 549, CEP: 79074-460, Campo Grande- MS -Brasil.
(2)
Instituto de Biociências de Botucatu - Universidade Estadual Paulista –UNESP.
Botucatu – SP.
* [email protected]
ABSTRACT
The controlled release systems (CRS) are intended to extend and enhance drug
delivery, allowing reduction of the dose and hence a reduction in drugs side effects.
This paper aims to contribute to the development of drug CRS for the treatment of
diseases like cancer. Thus, mesoporous silica matrices were synthesized and the
flavonoid quercetin was incorporated. This natural drug is known for its variety of
reported biological activities, including antioxidant and anti-inflammatory. The
synthesized particles were characterized by small angle X-ray scattering, infrared
absorption spectroscopy and transmission electron microscopy. The results show
that the synthesized particles have a hexagonal structure of pores and that the drug
incorporation was succeed, which enable the use of such particles as a drug CRS.
Keywords: controlled drug release, mesoporous silica, quercetin.
INTRODUCTION
The progress in research related to mesoscopic self-organized materials
marked the beginning of different uses for these systems, including studies of
controlled release of bioactive substances and drugs, better known as "drug delivery
systems". Among these mesoscopic organized materials, mesoporous silica has
contributed to this research once it present very interesting features as possessing
large surface area, stable pore structure and size and volume pore can be adjusted
according to the substance to be studied. The great interest in this type of research
relates to achieve an efficient system to control release of drugs in the treatment of
various diseases, without releasing the drug before the target location in the body is
reached [1-3].
The possibility of a combination of controlled drug delivery and biocompatible
properties of mesoporous silica has great advantages once silica can induce
bioactivity through its extrinsic properties and along with it it’s possible to fill the pores
with natural or synthetic compounds which are biological agents. Silica has a porous
network with different diameters and extensions that provide the possibility of hosting
different molecules. The wall structures of silica pores are formed by a disordered
network of free silanol groups and silane bonds that act as reactive nuclei and can be
hosts for chemical species [4-7].
This paper aims to contribute to the development of drug controlled release
systems for the treatment of diseases like cancer. Thus, mesoporous silica matrix
type MCM-41 were synthesized and characterized the flavonoid quercetin (C15H10O7)
was incorporated to the particles. This substance has many reported activities,
including antioxidant, anti-inflammatory and results of in vitro experiments and
preliminary tests in animals and humans that showed that quercetin inhibits tumor
growth [8-10].
EXPERIMENTAL
The synthesis of mesoporous silica was adapted from reference [11], wherein in
a round bottom flask of 125 mL, were added 96 mL of distilled water, 0.2 g of the
surfactant cetyltrimethylammonium bromide, CTAB (Sigma Life Science 98%) and
280 mL of Sodium hydroxide, NaOH (97% Químios P). After dissolution, the mixture
was placed under constant stirring for 30 min and then warmed up to 80 °C. Upon
reaching the desired temperature, to this mixture was added 1.34 mL of
tetraethoxysilane TEOS (Sigma Aldrich 98%). The mixture was left under stirring for
2 hours, maintaining the temperature of 80 °C. After this time, heating and stirring
were turned off and the mixture was allowed to stand to reach room temperature.
Them the reaction went to the centrifugation process where it was washed with MilliQ water for 3 times at 4500 rpm for 30 minutes each time. After centrifugation, the
pelleted material was taken to dryness in the oven with the temperature around 70 °C
for 12 hours and then to the muffle for heat treatment process to complete removal of
the surfactant. The temperature was increased in order of 1 °C per minute until
reaching 500 °C, and finally left at this temperature for 5 hours.
A solution of quercetin (~95% Sigma Aldrich) in ethanol (Vetec) at a
concentration of 22 mmol/L was prepared. The impregnation of quercetin in
mesoporous silica was made using a dilution of the quercetin solution at a
concentration of 5 mmol/L. To this solution was added 0.05 g of silica and it was
taken to stir for 24 hours at room temperature. After this time the solution was filtered
through filter paper and the particles were dried at room temperature.
RESULTS AND DISCUSSION
The removal of surfactant from silica was performed by two procedures,
washing with ultrapure water and calcination, which were followed by infrared
vibrational spectroscopy (FTIR). The FTIR spectra of silica synthesized in the form of
washed and calcined powder are shown in Figure 1. Can be observed in the spectral
range between 1226 cm-1 and 1067 cm-1 for the silica without heat treatment (SWT)
and in 1095 cm-1 for the calcined silica (CS) asymmetric stretching vibrations
associated to Si-O-Si bond in structure. The bands at 794 cm-1 in SWT and 800 cm-1
on CS are related to the symmetric stretching Si-O-Si. The broad bands at 3413 cm-1
in SWT and 3445 cm-1 in CS were attributed to the symmetric and asymmetric
stretching of OH of silanol groups as well as water on the external surface. The
bands in 1643 cm-1 in SWT and 1634 cm-1 in CS were ascribed as OH bending of
due to water molecules. The bands at 965 cm-1 in both samples correspond to the
angular deformation Si-OH. In SWT, bands at 2921 and 2850 cm-1 (C-H stretching)
and also 1485 cm-1 (C-H bending) are related to molecules of surfactant CTAB and,
therefore, they are not present on CS, once the calcination completely removed the
surfactant.
Fig. 1. FTIR spectra of: (a) mesoporous silica without heat treatment; (b) calcined
silica.
Analysis by small angle X-ray scattering (SAXS) shows how the pore structure
is organized. Can be observed in Figure 2 that pure mesoporous silica presents
hexagonal structure with three well defined peaks positioned at d 1 (100), d2 (110) and
d3 (200). The sample of silica with quercetin also shows the same peaks, but with a
lower intensity. This might be due to the fact that the pores of the silica are more
closed after impregnation with quercetin. A very important fact is that after
impregnation no peak shift occurred, i.e. no change in the structure formed. Through
these three peaks the correlation distance of the center of a single pore to another
can be calculate: for pure silica values obtained were 3.59 nm for d1, 2.06 nm for d2
and 1.79 nm for d3, while for silica impregnated with quercetin were 3.54 nm d1, 2.04
nm for d2 and for d3 1.79 nm.
Fig. 2: SAXS spectra of pure silica (a) and silica impregnated with quercetin (b).
Analysis of samples of mesoporous silica by transmission electron microscopy
confirmed the mesoporous feature of the material. In the images can see that when
the incidence of the electron beam occurs perpendicularly to the pore axis, is
possible see that these are homogenous (Figure 3a). However, when the incidence
of the electron beam is parallel to the pores axis in relation to the orientation of the
silica channels, can be observed that they have a slightly hexagonal shape in their
structure (Figure 3.b). Moreover, mesoporous silica nanoparticles have some small
agglomerates and their size varies from 50 to 100 nm.
a
b
Fig. 3: a) focusing the electron beam perpendicularly to the silica channels, b)
focusing the electron beam parallel to the silica channels.
CONCLUSION
After calcination the surfactant CTAB was removed from the silica, thus the
pores were free for the incorporation of the flavonoid quercetin. The synthesized
silica, after its characterization, proved to possess pore structures arranged in a
hexagonal porous network and be within the nanoscale. It was possible to
impregnate the silica with quercetin.
The most important characteristic of this material is its free pores, making it an
excellent candidate for drug carrier for controlled release study for the treatment of
diseases like cancer.
REFERENCES
1. SOUZA, K. C.; ARDISSON, J. D.; SOUSA, E. M. B. Study of mesoporous
silica/magnetite systems in drug controlled release. Journal of Materials ScienceMaterials in Medicine, v. 20, p. 507-512, 2009.
2. VIVERO-ESCOTO, J. L.; SLOWING, I.I.; TREWYN, B. G.; LIN, V. S.-Y.
Mesoporous Silica Nanoparticles for Intracellular Controlled. Small, v.6, n.18, p.
1952–1967, 2010.
3. SOUZA, A. Híbridos de Gel Polimérico em Sílica Mesoporosa
Estruturalmente Ordenada para Liberação Controlada de Fármacos. 2009, 28p.
Tese (Doutorado em Engenharia Química) - Universidade Federal de Minas Gerais–
UFMG, Belo Horizonte-MG.
4. ESPUELAS, S. Delivery systems for the treatment and prevention of
leishmaniosis. Gazeta Médica da Bahia, v.79, p. 134-146, 2009.
5. BELYAKOVA, L.A.; VARVARIN, A.M. Surfaces properties of silica gels modified
with hydrophobic groups. Colloids and Surfaces A: Physicochem. Eng. Aspects,
v.154 p. 285–294, 1999.
6. HORCAJADA, P.; RÁMILA, A.; PÉREZ-PARIENTE, J.; VALLET-REGI, M.
Influence of pore size of MCM-41 matrices on drug delivery rate. Microporous and
Mesoporous Materials, v.68 n.1-3, p. 105-109, 2004.
7. SLOWING, I.I.; VIVERO-ESCOTO, J. L.; Wu, C. W.; LIN, V. S.-Y. Mesoporous
silica nanoparticles as controlled release drug delivery and gene transfection carriers.
Advanced Drug Delivery, v.60, p. 1278–1288, 2008.
8. BEHLING, E. B.; SENDÃO, M. C.; FRANCESCATO, H. D. C.; ANTUNES, L. M.
G.; BIANCHI, M. L. P. Flavonóide quercetina : Aspectos gerais e ações biológicas.
Alimentos e Nutrição, v.15, p. 285-292, 2004.
9. CURCIO, M.; CIRILLO, G.; PARISI, O.L.; IEMMA, F.; PICCI, N.; PUOCI.
Quercetin-imprinted nanospheres as novel drug delivery devices. Journal of
functional Biomaterials. v.3, p. 269-282, 2012.
10. NIJVELDT, R.J.; NOOD, E.; HOORN, D.E.C.; BOELENS, P.G.; NORREN, K.;
LEEUWEN, P.A.M. Flavonoids: a review of probable mechanisms of action and
potential applications1–3. American Journal of Clinical Nutrition, v. 74, p. 418-425,
2001.
11. CHEN, H.; HE, J. Fine control over the morphology and structure of mesoporous
silica nanomaterials by a dual-templating approach. Chem. Commun., p. 4422-4424,
2008.