Magnetic fluid hyperthermia has been recently considered as a Renaissance of cancer treatment modality due to its remarkably low side effects and high treatment efficacy compared to conventional chemotheraphy or radiotheraphy. However, insufficient AC induction heating power at a biological safe range of AC magnetic field (H ·f < 3.0-5.0 × 10 A m s ), and highly required biocompatibility of superparamagnetic nanoparticle (SPNP) hyperthermia agents are still remained as critical challenges for successful clinical hyperthermia applications. Here, newly developed highly biocompatible magnesium shallow doped γ-Fe O (Mg -γFe O ) SPNPs with exceptionally high intrinsic loss power (ILP) in a range of 14 nH m kg , which is an ≈100 times higher than that of commercial Fe O (Feridex, ILP = 0.15 nH m kg ) at H ·f = 1.23 × 10 A m s are reported. The significantly enhanced heat induction characteristics of Mg -γFe O are primarily due to the dramatically enhanced out-of-phase magnetic susceptibility and magnetically tailored AC/DC magnetic softness resulted from the systematically controlled Mg cations distribution and concentrations in octahedral site Fe vacancies of γ-Fe O instead of well-known Fe O SPNPs. In vitro and in vivo magnetic hyperthermia studies using Mg -γFe O nanofluids are conducted to estimate bioavailability and biofeasibility. Mg -γFe O nanofluids show promising hyperthermia effects to completely kill the tumors.
Magnetic particle dipole interaction was revealed as a crucial physical parameter to be considered in optimizing the ac magnetically induced heating characteristics of magnetic nanoparticles. The ac heating temperature of soft MFe2O4 (M=Mg,Ni) nanoparticles was remarkably increased from 17.6 to 94.7 °C (MgFe2O4) and from 13.1 to 103.1 °C (NiFe2O4) by increasing the particle dipole interaction energy at fixed ac magnetic field of 140 Oe and frequency of 110 kHz. The increase in “magnetic hysteresis loss” that resulted from the particle dipole interaction was the main physical reason for the significant improvement of ac heating characteristics.
Self-heating temperature rising characteristics, cytotoxicity, and magnetic properties of NiFe2O4 nanoparticles have been investigated to confirm the effectiveness as an in vivo hyperthermia agent in biomedicine. NiFe2O4 nanoparticles showed both superparamagnetic and ferrimagnetic behaviors depending on particle sizes. The quantitative cytotoxicity test verified that both uncoated and chitosan-coated NiFe2O4 nanoparticles had noncytotoxicity. The solid state 35nm size NiFe2O4 nanoparticles first exhibited a maximum self-heating temperature of 44.2°C at H0f=5.1×108Am−1s−1. The physical nature of the self-heating was primarily thought to be due to the magnetic hysteresis loss, Neel rotations, and Brownian rotations of 35nm size NiFe2O4 nanoparticles.
Magnetic and AC magnetically induced heating characteristics of Fe 3 O 4 nanoparticles (IONs) with different mean diameters, d, systematically controlled from 4.2 to 22.5 nm were investigated to explore the physical relationship between magnetic phase and specific loss power (SLP) for hyperthermia agent applications. It was experimentally confirmed that the IONs had three magnetic phases and correspondingly different SLP characteristics depending on the particle sizes. Furthermore, it was demonstrated that pure superparamagnetic phase IONs (d < 9.8 nm) showed insufficient SLPs critically limiting for hyperthermia applications due to smaller AC hysteresis loss power (Néel relaxation loss power) originated from lower out-of-phase magnetic susceptibility. V C 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3689751]In recent, superparamagnetic Fe 3 O 4 nanoparticles (SPIONs) have been paid considerable attentions for a local hyperthermia agent in nanomedicine due to its officially approved high biocompatibility. 1 Accordingly, various technical and engineering approaches, i.e., developing various synthesis methods, controlling particle dipole-dipole interaction and particle dispersion status in ferrofluidics, and studying the effects of Fe 2þ /Fe 3þ ion distributions on heating ability etc., have been and are being made to improve the AC magnetically induced heating characteristics and the relevant magnetic properties of SPIONs for theragonosis agent applications. [2][3][4] For the applications to an in-vivo magnetic fluidic hyperthermia agent, magnetic nanoparticles should have pure superparamagnetic phase for easy transportation, good circulation, and no agglomeration in the blood vessel as well as have a smaller particle size, d < 7 9 nm, with a narrow size distribution (<10%) for both effective injection, i.e., intravenous injection, intraarterial injection, or intratumoral injection, into and excretion from human body. 5 In particular, they should produce a heat generation as high as possible at a small concentration (a higher specific loss power (SLP)) in the biological safe and physiologically tolerable range of the applied magnetic field (H appl < 190 Oe) and frequency (f appl < 120 kHz) to completely necrotize tumors with minimized systemic "side effects." 6-9 Considering these biotechnical requirements, the SPIONs reported so far have critical challenges for a hyperthermia agent, because the magnetic phase (intrinsic magnetic property) of the developed SPIONs is not well defined and has strong dependence on the particle sizes as well as correspondingly wide distribution of SLP values (5 500 W/g). 2-4,10 Therefore, systematic studies on the magnetic nature and the AC heating characteristics of IONs accurately controlled the particle sizes are essentially required to evaluate the biotechnical feasibility of IONs, particularly SPIONs, for a clinical hyperthermia agent in nanomedicine.In this letter, we investigated the magnetic properties and the AC heating characteristics of IONs with differ...
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