Examining the effect of ions and proteins on the heat dissipation of iron oxide nanocrystals

Inductive Heating Enhances Ripening in the Aqueous Synthesis of Magnetic Nanoparticles

The search for competitive processes and products using environmentally friendly chemistry is, nowadays, one of the greatest challenges in materials science. In this work, we explore the influence of magnetic inductive heating on the synthesis of magnetic iron oxide nanoparticles in water, either by the coprecipitation of iron(II) and iron(III) salts or by the oxidative precipitation of an iron(II) salt. In the first case, the way the heat is transmitted to the system influences mainly the nanoparticle growth that is thermally activated reaching nanoparticles up to 16 nm. In the second case, it influences magnetic nanoparticle nucleation through the dissolution of the initial iron oxyhydroxide formed (the Green Rust) and the crystallization of magnetic iron oxide leading to nanoparticles up to 55-64 nm. This nonconventional heating method can produce monodisperse populations (size distribution <25%) of bigger magnetic iron oxide nanoparticles if the appropriate magnetic field conditions are used. The results were interpreted as an enhancement of the oriented attachment growth mechanism by the use of inductive heating, and suggest the possibility of increasing the size range of nanomaterials that can be obtained by sustainable aqueous routes using nonconventional heating, while maintaining low size dispersity.

Influence of the Aspect Ratio of Iron Oxide Nanorods on Hysteresis-Loss-Mediated Magnetic Hyperthermia

Owing to the problems associated with conventional cancer treatment methods, magnetic hyperthermia-based cancer therapy has gained importance recently. Achieving the desired heating effect at the site of the tumor with a minimal concentration of iron oxide nanoparticles (IONPs) and a safer field is necessary to explore the advantages of hyperthermia. For one to address this challenge, biocompatible IONPs with a desirable magnetic response at a tolerable field are necessary. In this work, magnetic shape anisotropy of iron oxide nanorods (NR) of different lengths (70, 115, 170, and 210 nm) with different aspect ratios ranging from 1.55 to 3.2 was explored to achieve higher hysteresis loss, in turn leading to better hyperthermia efficiency. The magnetic properties of the NRs with respect to the applied field were studied using micromagnetic simulation. Even though the nanorods with high aspect ratio showed a higher hysteresis loss of 69485 J/m3 at 2000 Oe, the field required to attain it was high and well beyond the safety limit. From nanorods of various aspect ratios, the nanorod with a lower aspect ratio of 1.55 and a length of 70 nm exhibited a better hysteresis loss and specific absorption rate (SAR) value of 4214 W g-1 was achieved at a frequency and alternating magnetic field of 400 kHz and 800 Oe, respectively. The PEGylated GO-Nanorod of 70 nm exhibited excellent antitumor efficacy in 4T1 tumor model mice by obstructing the tumor progression within a safer dosage and field.