Fe²⁺ Deficiencies, FeO Subdomains, and Structural Defects Favor Magnetic Hyperthermia Performance of Iron Oxide Nanocubes into Intracellular Environment

Abstract

Herein, by studying a stepwise phase transformation of 23 nm FeO-Fe3O4 core-shell nanocubes into Fe3O4, we identify a composition at which the magnetic heating performance of the nanocubes is not affected by the medium viscosity and aggregation. Structural and magnetic characterizations reveal the transformation of the FeO-Fe3O4 nanocubes from having stoichiometric phase compositions into Fe 2+ deficient Fe3O4 phases. The resultant nanocubes contain tiny compressed and randomly distributed FeO sub-domains as well as structural defects. This phase transformation causes a tenfold increase in the magnetic losses of the nanocubes, which remains exceptionally insensitive to the medium viscosity as well as aggregation unlike similarly sized single-phase magnetite nanocubes. We observe that the dominant relaxation mechanism switches from Néel in fresh core-shell nanocubes to Brownian in partially oxidized nanocubes and once again to Néel in completely treated nanocubes. The Fe 2+ deficiencies and structural defects appear to reduce the magnetic energy barrier and anisotropy field, thereby driving the overall relaxation into Néel process. The magnetic losses of the particles remain unchanged through a progressive internalization/association to ovarian cancer cells. Moreover, the particles induce a significant cell death after being exposed to hyperthermia treatment. Here, we present the largest heating performance that has been reported to date for 23 nm iron oxide nanoparticles under cellular and intracellular conditions. Our findings clearly demonstrate the positive impacts of the Fe 2+ deficiencies and structural defects in the Fe3O4 structure on the heating performance under cellular and intracellular conditions.

Internal Structure and Magnetic Properties in Cobalt Ferrite Nanoparticles: Influence of the Synthesis Method

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Recent Progress in Ferroptosis Inducers for Cancer Therapy

“…The catalytic activity of ferrous iron (Fe 2+ ) is several magnitudes higher than that of ferric iron (Fe 3+ ) . However, the intracellular Fe 2+ level remains low . Inspired by the industrial Electro‐Fenton technology, Liu et al developed a nano‐engineering method by depositing Fe 3+ and tannic acid (TA) onto the nanocrystal of SRF .…”

Field Dependence of Magnetic Disorder in Nanoparticles

“…These have a pivotal importance for the diverse technological applications of magnetic nanoparticles, such as in recording media [12], biomedicine [13][14][15], catalysis [16], or battery materials [17]. The impact of disorder on the heating performance of magnetic nanoparticles has recently been demonstrated [18][19][20]. However, despite the great technological relevance and fundamental importance, the three-dimensional magnetic configuration and the nanoscale distribution of spin disorder within magnetic nanoparticles remain a key challenge.…”