Biocompatible Magnetic Fluids of Co-Doped Iron Oxide Nanoparticles with Tunable Magnetic Properties

Abstract

Magnetite (Fe3O4) particles with a diameter around 10 nm have a very low coercivity (Hc) and relative remnant magnetization (Mr/Ms), which is unfavorable for magnetic fluid hyperthermia. In contrast, cobalt ferrite (CoFe2O4) particles of the same size have a very high Hc and Mr/Ms, which is magnetically too hard to obtain suitable specific heating power (SHP) in hyperthermia. For the optimization of the magnetic properties, the Fe2+ ions of magnetite were substituted by Co2+ step by step, which results in a Co doped iron oxide inverse spinel with an adjustable Fe2+ substitution degree in the full range of pure iron oxide up to pure cobalt ferrite. The obtained magnetic nanoparticles were characterized regarding their structural and magnetic properties as well as their cell toxicity. The pure iron oxide particles showed an average size of 8 nm, which increased up to 12 nm for the cobalt ferrite. For ferrofluids containing the prepared particles, only a limited dependence of Hc and Mr/Ms on the Co content in the particles was found, which confirms a stable dispersion of the particles within the ferrofluid. For dry particles, a strong correlation between the Co content and the resulting Hc and Mr/Ms was detected. For small substitution degrees, only a slight increase in Hc was found for the increasing Co content, whereas for a substitution of more than 10% of the Fe atoms by Co, a strong linear increase in Hc and Mr/Ms was obtained. Mössbauer spectroscopy revealed predominantly Fe3+ in all samples, while also verifying an ordered magnetic structure with a low to moderate surface spin canting. Relative spectral areas of Mössbauer subspectra indicated a mainly random distribution of Co2+ ions rather than the more pronounced octahedral site-preference of bulk CoFe2O4. Cell vitality studies confirmed no increased toxicity of the Co-doped iron oxide nanoparticles compared to the pure iron oxide ones. Magnetic heating performance was confirmed to be a function of coercivity as well. The here presented non-toxic magnetic nanoparticle system enables the tuning of the magnetic properties of the particles without a remarkable change in particles size. The found heating performance is suitable for magnetic hyperthermia application.

Coating Effect on the 1H—NMR Relaxation Properties of Iron Oxide Magnetic Nanoparticles

“…[ 27 ]. Ideally, these nanosystems could selectively reach the targeted tissues and organs, increase the image contrast and, at the same time, release a drug or heat that region (through Magnetic Fluid Hyperthermia [ 28 , 29 , 30 , 31 ]) to induce cell death. Thus, these nanoparticles can combine properties useful in diagnostics with other properties compatible with therapy, thus becoming potential theranostic agents.…”

Магнитные нанокомпозиты оксид графена/магнетит + кобальтовый феррит (GrO/Fe-=SUB=-3-=/SUB=-O-=SUB=-4-=/SUB=- + CoFe-=SUB=-2-=/SUB=-O-=SUB=-4-=/SUB=-) для магнитной гипертермии

“…Величины изомерных сдвигов приведены относительно металлической фольги α-Fe при комнатной температуре. [12]. Помимо скошенного состояния спинов, за уменьшение намагниченности могут быть ответственны поверхностные эффекты и эффекты размерности частиц [60].…”

“…НЧ феррита-шпинели CoFe 2 O 4 по сравнению с магнетитом менее токсичны и рассматриваются как перспективный материал для биомедицинских применений благодаря своим высоким магнитным характеристикам, монодисперсности, однородности физико-химических свойств и биосовместимости [5][6][7][8][9][10]. Токсичность НЧ может быть устранена нанесением на их поверхности нетоксичных биологически совместимых материалов [5,10,11], а также созданием нанокомпозитов Fe 3 O 4 −CoFe 2 O 4 [12], НЧ типа наностержней [13] или НЧ типа ядро/оболочка Fe 3 O 4 /CoFe 2 O 4 [14][15][16][17][18].…”

Computer Simulations of Dynamic Response of Ferrofluids on an Alternating Magnetic Field with High Amplitude

“…Colloidal suspensions of magnetized nanoparticles in liquid nonmagnetic carriers are known as ferrofluids. The ability of ferrofluids to respond to external magnetic fields makes them useful in many areas, ranging from engineering [4], to biomedical applications [5,6]. Such materials can be used as an active medium in devices (sealants, heat conduction media, media for hydraulic suspensions) and in materials processing (separation media, gas-fluidized beds).…”