Silica encapsulated manganese perovskite nanoparticles for magnetically induced hyperthermia without the risk of overheating

Abstract

Nanoparticles of manganese perovskite of the composition La(0.75)Sr(0.25)MnO(3) uniformly coated with silica were prepared by encapsulation of the magnetic cores (mean crystallite size 24 nm) using tetraethoxysilane followed by fractionation. The resulting hybrid particles form a stable suspension in an aqueous environment at physiological pH and possess a narrow hydrodynamic size distribution. Both calorimetric heating experiments and direct measurements of hysteresis loops in the alternating field revealed high specific power losses, further enhanced by the encapsulation procedure in the case of the coated particles. The corresponding results are discussed on the basis of complex characterization of the particles and especially detailed magnetic measurements. Moreover, the Curie temperature (335 K) of the selected magnetic cores resolves the risk of local overheating during hyperthermia treatment.

Adiabatic magnetothermia makes possible the study of the temperature dependence of the heat dissipated by magnetic nanoparticles under alternating magnetic fields

“…The SAR of ferromagnetic MNPs can be determined from minor magnetization loops. [4][5][6] This method cannot be, however, applied to superparamagnetic nanoparticles, which do not show hysteresis loops, but SAR can be obtained from the measurement of the out-of-phase ac magnetic susceptibility, Љ, by using the theoretical expressions that relate both magnitudes. 7 One drawback of the latter method is that, due the characteristics of the currently used setups, Љ is often measured with acfield parameters different than those used for MFH.…”

Manganese Perovskite Nanoparticles and the Downturn of Inverse Susceptibility above the Curie Temperature

“…The SQUID magnetometer measurements were performed on the manganite La 0.75 Sr 0.25 MnO 3 in the form of the bulk sample (LSMOB) and two 20 nm nanoparticle samples LSMO and LSMO@SiO 2 , where the second one was encapsulated in SiO 2 [2]. The temperature dependence of the magnetization M under the applied field 7.95 kA/m was measured when cooling the sample from 400 to 300 K. Well above T c , M can be separated to a Curie-Weiss (C-W) part and a small contribution M imp arising from ferromagnetic impurities.…”

UV Light Effects on Proteins: From Photochemistry to Nanomedicine

“…Lee et al, 2011). However, in order to avoid the risk of overheating during the hyperthermia effect, curie temperature tuning is done by designing the composition of the core magnetic nanoparticles (Kaman et al, 2009).…”