Avaliação experimental e teórica da hipertermia magnética de magnetolipossomos para tratamento oncológico
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2016-08-17
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Universidade Federal de Goiás
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In this work we investigated the magnetothermal efficacy of two nanocarriers, magnetic fluids
(MF) and magnetoliposomes (ML), with potential for oncology therapy. Ferrofluids based on
manganese ferrite nanoparticles, surface coated with citric acid, were synthesized.
Magnetoliposomes, vesicles containing magnetic nanoparticles inside, were prepared by the
extrusion method. X-ray diffraction corfimed the spinel structure, while transmission electron
microscopy revealed spherical nanoparticles with a lognormal size distribution and mean diameter
of (11,1 ± 3,5) nm. Magnetization curves, at quasi-static conditions revealed particles at the
superparamagnetic regime. A reduction in the saturation magnetization in comparison with bulk
samples were explained by a nonmagnetic shell with thickness of 1.1 nm. The concentration and
particle size distribution of the liposomes (mean diameter of 180 nm) were obtained from the
nanoparticle tracking analysis (NTA). The combination of magnetometry and NTA data revealed
an encapsulation particle volume fraction in the range of 0.26 to 0.83% for the samples. Magnetic
birefringence data showed a higher fraction of aggregates in ML in comparison to MF. Magnetic
hyperthermia experiments were perfomed at distinct frequencies (111 -632 kHz) and field
amplitudes (up to 250 Oe) for distinct ML and MF samples. In general, we found a reduction of
magnetothermal efficacy for magnetoliposomes when compared to MF. although the effect is less
evident at lower frequencies (<170 kHz). The explanation was obtained through a new theoretical
model that, not only takes into account the effect of dipolar interaction in the magnetic anisotropy,
but also the reduction of susceptibility due to blocked nanoparticles. This contribution was shown
to be strongly dependent upon field frequency, amplitude and aggregates in the suspension.
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SILVA, Anderson Costa da. Avaliação experimental e teórica da hipertermia magnética de magnetolipossomos para tratamento oncológico. 2015. 137 f. Tese (Doutorado em Física) - Universidade Federal de Goiás, Goiânia, 2016.