Distinguishing between heating power and hyperthermic cell-treatment efficacy in magnetic fluid hyperthermia

In the magnetic fluid hyperthermia (MFH) research field, it is usually assumed that achieving a uniform temperature enhancement (ΔT) of the entire tumour is a key-point for treatment. However, various experimental works reported successful cell apoptosis via MFH without a noticeable ΔT of the system. A possible explanation of the success of these negligible-ΔT experiments is that a local ΔT restricted to the particle nanoenvironment (i.e. with no significant effect on the global temperature T) could be enough to trigger cell death. Shedding light on such a possibility requires accurate knowledge of heat dissipation at the local level in relation to the usually investigated global (average) one. Since size polydispersity is inherent to all synthesis techniques and the heat released is proportional to the particle size, heat dissipation spots with different performances-and thus different effects on the cells-will likely exist in every sample. In this work we aim for a double objective: (1) to emphasize the necessity to distinguish between the total dissipated heat and hyperthermia effectiveness, and (2) to suggest a theoretical approach on how to select, for a given size polydispersity, a more adequate average size so that most of the particles dissipate within a desired heating power range. The results are reported in terms of Fe3O4 nanoparticles as a representative example

The role of size polydispersity in magnetic fluid hyperthermia: average vs. local infra/over-heating effects

An efficient and safe hyperthermia cancer treatment requires the accurate control of the heating performance of magnetic nanoparticles, which is directly related to their size. However, in any particle system the existence of some size polydispersity is experimentally unavoidable, which results in a different local heating output and consequently a different hyperthermia performance depending on the size of each particle. With the aim to shed some light on this significant issue, we have used a Monte Carlo technique to study the role of size polydispersity in heat dissipation at both the local (single particle) and global (macroscopic average) levels. We have systematically varied size polydispersity, temperature and interparticle dipolar interaction conditions, and evaluated local heating as a function of these parameters. Our results provide a simple guide on how to choose, for a given polydispersity degree, the more adequate average particle size so that the local variation in the released heat is kept within some limits that correspond to safety boundaries for the average-system hyperthermia performance. All together we believe that our results may help in the design of more effective magnetic hyperthermia applications.This work was co-financed by the EU (project FEMTOSPIN, Ref. NNP3-SL-2012-281043), the Spanish MEC (FIS2010-20979-C02-02 and MAT2009-08165) and Xunta de Galicia (INCITE 08PXIB236052PR). D.S. acknowledges Xunta de Galicia (Spain) for financial support under the Plan I2C. The FPI Spanish program supported I. C-L

The role of size polydispersity in magnetic fluid hyperthermia: average vs. local infra/over-heating effects

This is the accepted manuscript of the following article: Munoz-Menendez, C., Conde-Leboran, I., Baldomir, D., Chubykalo-Fesenko, O., & Serantes, D. (2015). The role of size polydispersity in magnetic fluid hyperthermia: average vs. local infra/over-heating effects. Physical Chemistry Chemical Physics, 17(41), 27812-27820. doi: 10.1039/c5cp04539hAn efficient and safe hyperthermia cancer treatment requires the accurate control of the heating performance of magnetic nanoparticles, which is directly related to their size. However, in any particle system the existence of some size polydispersity is experimentally unavoidable, which results in a different local heating output and consequently a different hyperthermia performance depending on the size of each particle. With the aim to shed some light on this significant issue, we have used a Monte Carlo technique to study the role of size polydispersity in heat dissipation at both the local (single particle) and global (macroscopic average) levels. We have systematically varied size polydispersity, temperature and interparticle dipolar interaction conditions, and evaluated local heating as a function of these parameters. Our results provide a simple guide on how to choose, for a given polydispersity degree, the more adequate average particle size so that the local variation in the released heat is kept within some limits that correspond to safety boundaries for the average-system hyperthermia performance. All together we believe that our results may help in the design of more effective magnetic hyperthermia applicationsThe authors thank the Centro de Supercomputación de Galicia (CESGA) for the computational facilities. This work was co-financed by the EU (project FEMTOSPIN, Ref. NNP3-SL-2012-281043), the Spanish MEC (FIS2010-20979C02-02 and MAT2009-08165) and Xunta de Galicia (INCITE 08PXIB236052PR). D.S. acknowledges Xunta de Galicia (Spain) for financial support under the Plan I2C. The FPI Spanish program supported I. C-L.S

A single picture explains diversity of hyperthermia response of magnetic nanoparticles

Progress in the design of nanoscale magnets for localized hyperthermia cancer therapy has been largely driven by trial-and-error approaches, for instance, by changing of the stoichiometry composition, size, and shape of the magnetic entities. So far, widely different and often conflicting heat dissipation results have been reported, particularly as a function of the nanoparticle concentration. Thus, achieving hyperthermia-efficient magnetic ferrofluids remains an outstanding challenge. Here we demonstrate that diverging heat-dissipation patterns found in the literature can be actually described by a single picture accounting for both the intrinsic magnetic features of the particles (anisotropy, magnetization) and experimental conditions (concentration, magnetic field). Importantly, this general magnetic-hyperthermia scenario also predicts a novel non-monotonic concentration dependence with optimum heating features, which we experimentally confirmed in iron oxide nanoparticle ferrofluids by fine-tuning the particle size. Overall, our approach implies a magnetic hyperthermia trilemma that may constitute a simple strategy for development of magnetic nanomaterials for optimal hyperthermia efficiency.This work was partially supported by the EU (projects FEMTOSPIN, ref. NNP3-SL-2012-281043; and MULTIFUN, ref. 246479), the Spanish Ministry of Economy and Competitiveness (FIS2010-20979-C02-02, MAT2009-08165, MAT2011-23641, MAT2013-47395-C4-3-R, CONSOLIDER CSD2007-00041), Xunta de Galicia (INCITE 08PXIB236052PR and EM2013/037), and Gobierno de la Comunidad de Madrid (NANOFRONTMAG, S2013/MIT-2850). I.C.-L. (BES-2010-033138) acknowledges financial support from FPI subprogram. C.M.-B. (RYC-2008-02054) and F.J.T. (RYC-2011-09617) acknowledge financial support from the “Ramon y Cajal ́ ” subprogram

A Single Picture Explains Diversity of Hyperthermia Response of Magnetic Nanoparticles

Progress in the design of nanoscale magnets for localized hyperthermia cancer therapy has been largely driven by trial-and-error approaches, for instance, by changing of the stoichiometry composition, size, and shape of the magnetic entities. So far, widely different and often conflicting heat dissipation results have been reported, particularly as a function of the nanoparticle concentration. Thus, achieving hyperthermia-efficient magnetic ferrofluids remains an outstanding challenge. Here we demonstrate that diverging heat-dissipation patterns found in the literature can be actually described by a single picture accounting for both the intrinsic magnetic features of the particles (anisotropy, magnetization) and experimental conditions (concentration, magnetic field). Importantly, this general magnetic-hyperthermia scenario also predicts a novel non-monotonic concentration dependence with optimum heating features, which we experimentally confirmed in iron oxide nanoparticle ferrofluids by fine-tuning the particle size. Overall, our approach implies a <i>magnetic hyperthermia trilemma</i> that may constitute a simple strategy for development of magnetic nanomaterials for optimal hyperthermia efficiency