Síntese e caracterização de nanopartículas e nanocompósitos magnéticos para aplicações biomédicas

Abstract

The synthesis of nanostructured magnetic materials has been intensively researched because of their large field of applications as magnetic carriers in drug targeting, magnetic hyperthermia in tumor treatment, among others. In this work, we have explored the possibility of synthesizing three mesoporous series Si02-Fe304 nanocomposites. The first two sets of composites (A and B) were obtained by impregnation of an iron precursor into a silica framework. The proposed method involves the preparation of an iron oxide precursor in ethanol and the subsequent impregnation of SBA-15 and MCM-41 mesoporous hexagonal silica. Iron oxide was formed inside the porous structure, thus producing the magnetic device. The third type of nanocomposite (C series) was synthesized by sol-gel method and the iron oxide precursor was mixed during the mesoporous silica synthesis. The nanocomposites were characterized by X-ray diffraction (XRD), Mossbauer spectroscopy, Fourier- transformed infrared spectroscopy (FTIR), N2 adsorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Magnetic measurements (M-H and ZFC/FC M-T curves) were made using a SQUID magnetometer in the temperature range 8-270 K. Our results revealed a well ordered mesopore structure of the nanocomposites. The average size of magnetite particles obtained by XRD data was about 29 nm for nanocomposite of A and B series, and 10 nm for nanocomposite of C series. The average diameter of magnetic nanoparticles, obtained by magnetization data were higher, about 40 nm for nanocomposites of A series and about 39 nm for C series. Mossbauer spectroscopy showed that magnetite is produced with high purity in the applied synthesis route, except the route to obtaining the sample C3. The data of TEM had shown that the magnetic nanoparticles were well dispersed in the pores of silica. Measurements of AC magnetic-field-induced heating properties of the obtained nanocomposites under two different applied magnetic fields showed that the samples are suitable as a hyperthermia agent for biological applications. The results showed that the release system is dependent on the used drug. In the case of atenolol, a model drug used, the release was very dependent on the applied field. The influence of these magnetic particles in the release kinetic was studied using drugs like doxorubicin (DOX) and atenolol; this study was made under in vitro conditions. The release was studied in absence and presence of a external oscillating magnetic field. The kinetic mechanisms and diffusion models were investigated by the external field, and the results had showed a small influence of this parameter on the process of drug release of DOX, however, greatly influences the atenolol release. To explain this fact, aninteraction model between this drug and the nanocomposite was proposed. Finaly, cytotoxicity assays were performed, showing that the C3 nanocomposite showed toxicity for the four cell lines tested.Keywords Mesoporous materials, nanocomposites, magnetite, magnetic hyperthermia.