Confining iron oxide nanocubes inside submicrometric cavities as a key strategy to preserve magnetic heat losses in an intracellular environment

The design of magnetic nanostructures whose magnetic heating efficiency remains unaffected at the tumor site is a fundamental requirement to further advance magnetic hyperthermia in clinic. This work demonstrates that the confinement of magnetic nanoparticles (NPs) into a submicrometric cavity is a key strategy to enable a certain degree of nanoparticle motion and minimize aggregation effects, consequently preserving the magnetic heat loss of iron oxide nanocubes (IONCs) under different conditions, including intracellular environments. We fabricated magnetic Layer-by-Layer (LbL) self-assembled polyelectrolyte submicrometric capsules using three different approaches, and we studied their heating efficiency as obtained in aqueous dispersions and once internalized by tumor cells. First, IONCs were added to the hollow cavities of LbL submicrocapsules, allowing the IONCs to move to a certain extent in the capsule cavities. Second, IONCs were co-encapsulated into solid calcium carbonate cores coated with LbL po...