High performance multi-core iron oxide nanoparticles for magnetic hyperthermia: microwave synthesis, and the role of core-to-core interactions

Abstract

The adoption of magnetic hyperthermia as either a stand-alone or adjunct therapy for cancer is still far from being optimised due to the variable performance found in many iron oxide nanoparticle systems, including commercially available formulations. Herein, we present a reproducible and potentially scalable microwave-based method to make stable citric acid coated multi-core iron oxide nanoparticles, with exceptional magnetic heating parameters, viz. intrinsic loss parameters (ILPs) of up to 4.1 nH m(2) kg(-1), 35% better than the best commercial equivalents. We also probe the core-to-core magnetic interactions in the particles via remanence-derived Henkel and ΔM plots. These reveal a monotonic dependence of the ILP on the magnetic interaction field Hint, and show that the interactions are demagnetising in nature, and act to hinder the magnetic heating mechanism.

Low toxic maghemite nanoparticles for theranostic applications

“…The precipitate was separated by centrifugation at 22,000 rpm for 40 min, which was then followed by multiple washing by means of bidistilled water and drying at 40°C in a vacuum chamber overnight. 16 …”

“…Magnetic nanoparticles were synthesized by means of the microwave-assisted coprecipitation using the modified scheme of Blanco-Andujar et al 16 The synthesis was carried out as follows. A solution of 1,112 g of FeSO 4 ⋅6H 2 O (II) and 21,624 g of FeCl 3 ⋅6H 2 O with 40 mL of water was obtained.…”

Magnetic iron oxide nanoparticles: Recent trends in design and synthesis of magnetoresponsive nanosystems

“…For example, a stoichiometric Fe(II) and Fe(III) salt mixture was hydrolysed in the mixture of diethylene glycol (DEG) and N-methyldiethanolamine (NMDA) at high temperature over the longer period to allow clustering and coalescence of the preformed seeds [76]. A similar, coprecipitation preparation strategy can be found in the latest literature [77].…”

“…It was suggested a straightforward route of physicochemical (iron dissolution) and colloidal (pH-dependent charging and particle size, salt tolerance from coagulation kinetics) measurements to assess eligibility of IONPs for biomedical tests [18]. The biomedical use of citrated IONPs is favored in literature (e.g., the famous VSOP-C184 product in [3,7,28] or the very recent multi-core samples in [77]), however they coagulate much below the physiological salt concentration and even more the quantity of iron leaching from them is very high due to the reductive and complex forming ability of citric acid; the dissolved iron ions may cause oxidative stress besides the danger of particle aggregation in vivo.…”

“…Multiple iron oxide cores (maghemite nanoparticles) assembled as magnetically cooperative multi-core particles were obtained by applying a single-step high temperature hydrolysis procedure [76] and also by chemical coprecipitation in a microwave reactor [77]. Loading of liposomes with iron oxide nanoparticles [97], mostly clusters preformed from aqueous [51] and organic [98] ferrofluids, gives rise to magnetoliposomes with high magnetophoretic mobility and MRI contrast, proved to be very effective in drug and gene delivery into cancer cells in vitro and in vivo.…”