Olayo Valles, Roberto

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    Influence of interparticle magnetic interactions on heat dissipation in magnetic nanoparticles and magnetomicelles
    (2013) Olayo Valles, Roberto; Rinaldi, Carlos; College of Engineering; Torres Lugo, Madeline; Latorre Esteves, Magda; Juan García, Eduardo J.; Department of Chemical Engineering; López Moreno, Martha L.
    Magnetically actuated nanovectors are prepared through the combination of magnetic nanoparticles and thermoresponsive materials that facilitate the release of the drug when heated at a temperature slightly above the normal body temperature. When the nanovectors are subjected to an AC magnetic field the magnetic nanoparticles dissipate heat which increases the local temperature thus inducing the desired response from the thermoresponsive material. Several magnetically actuated nanovectors have been proposed but challenges such as leakage before the magnetic stimulus is applied, poor stability, and toxicity still exist. Additionally, the effect that the state of aggregation of the nanoparticles within these nanovectors has on heat dissipation has not been considered in their design. Magnetomicelles have been proposed as magnetically actuated nanovectors. Here the preparation of biocompatible magnetomicelles is presented and the effect of the molecular weight of the core-forming polymer block on the magnetic properties was studied. The magnetomicelles were magnetically characterized in liquid suspensions and embedded in a polymer matrix. The results show that as the molecular weight of the core-forming polymer block increases, both the interparticle magnetic interactions and specific absorption rate decrease. This is probably due to mixing between the polymer and the magnetic nanoparticles which increases the interparticle distance. Additionally, the effect of interparticle magnetic interactions on heat dissipation was studied for two types of magnetic nanoparticles: iron oxide and cobalt ferrite. These particles relax by different processes when subjected to an AC magnetic field. Thorough magnetic characterization was done to measure the characteristic parameters of each type of nanoparticle so that comparison could be made between experimentally measured and theoretically calculated heat dissipation. Each type of nanoparticle was synthesized in two manners: coprecipitation of precursor salts and thermal decomposition of a precursor oleate. The former produced aggregated nanoparticles while the latter produced dispersed non-interacting particles. The theoretical results agreed with experimentally measured heat dissipation of the non-interacting iron oxide nanoparticles but underestimated the heat dissipated by aggregated nanoparticles.