Multifunctional approaches based on thermal nanotherapies: heat generation, therapeutic efficiency and limitations

Thermal nanotherapies as magnetic hyperthermia (MHT) and photothermal therapy (PTT) are two promising emergent treatments and non-invasive approaches for tumor ablation, where localized heat generation is mediated by magnetic and photo-activatable nanomaterials [1]. Until very recently, these thermal nanotherapies, have been developed separately: MHT is mainly focused on the use of magnetic iron oxide nanoparticles due to their excellent biodegradability [2], while metallic nanoparticles such as gold nanomaterials are often preferred due to their strong absorption cross sections . They have recently begun to intersect due to the recent discovery and use of photothermal properties of iron oxide nanostructures or to the use of magneto-photothermal hybrids, which efficiently combine both heating features in one-single object.
A comprehensive comparison of the heating efficiency of magneto- versus photo-thermal effect is presented, where different magnetic nanoparticles have been confronted (iron oxides, cobalt ferrite, spheres, cubes, flowers) with different metallic nanoparticles in aqueous, cellular, and tumoral environment [3]. Intracellular processing markedly impacted MHT, while endosomal sequestration could have a positive effect for PTT. In the search for the most therapeutically viable modality, the effect of nanoparticle concentration and the experimental exposure parameters (magnetic field strengths/frequencies and laser power densities) have been investigated. Several combinations of thermal nanotherapies with other therapeutic nanofunctionalities will be presented.

References
[1] a) R. Hergt, S. Dutz, J. Magn. Magn. Mater. 2007, 311, 187; b) M. Garcia, Journal of Physics D: Applied Physics 2011, 44, 283001.
[2] a) A. G. Roca, et al., Adv. Drug Deliv. Rev. 2018; b) D. Cabrera, et al., ACS Nano 2018, 12, 2741.
[3] A. Espinosa, et al., Adv. Funct. Mater. 2018, 28, 1803660