Novel nanoparticles with Cr³⁺ substituted ferrite for self-regulating temperature hyperthermia

Abstract

For hyperthermia to be used under clinical conditions for cancer therapeutics the temperature regulation needs to be precise and accurately controllable. In the case of the metal nanoparticles used for such activities, a high coercivity is a prerequisite in order to couple more energy in a single heating cycle for efficient and faster differential heating. The chemically stable Co-Zn ferrite nanoparticles have typically not been used in such self-regulating hyperthermia temperature applications to date due to their low Curie temperature usually accompanied by a poor coercivity. The latter physical property limitation under clinically applied magnetic field conditions (frequency: 100 kHz, intensity: 200 Oe) restricts the transfer of a reasonable heat energy, and thus limits the hyperthermia efficiency. Here, we report a novel Cr substituted Co-Zn ferrite (ZnCoCrFeO), whose Curie temperature and coercivity values are 45.7 °C and 174 Oe, respectively. Under clinically acceptable magnetic field conditions, the temperature of these nanoparticle suspensions can be self-regulated to 44.0 °C and, most importantly with a specific absorption rate (SAR) of 774 W kg, which is two-fold higher than the SAR standard for magnetic nanoparticles used in hyperthermia (300 W kg). The evaluation of the in vitro cytotoxicity of the nanoparticles reports a low toxicity, which points to a novel set of magnetic nanoparticles for use in self-regulating hyperthermia.

Proposed use of self-regulating temperature nanoparticles for cancer therapy

“…For the intensity of 29.6 kA m −1 with a frequency of 104 kHz, Ferk et al reported a SAR of 3.9 W g −1 [11]. We have obtained a SAR of 0.776 W g −1 at an intensity of 16 kA m −1 with the frequency of 100 kHz [13]. For the Me 1-x ZnxFe 2 O 4 (Me = Ni, Cu, Co, Mn) nanoparticles, the SAR is not available [9].…”

“…Hejase [12]. We have recently found that the tetragonal Zn 0.54 Co 0.46 Cr 0.6 Fe 1.4 O 4 nanoparticles with the edge length around 30 nm exhibit a T c of 45.7°C [13].…”

“…For many of the low Curie temperature nanoparticles mentioned above, this information is still missing or the nanoparticles have low cytotoxicity [8][9][10][11]. The nanoparticles we developed do not exhibit cytotoxicity in vitro cell incubation [13]. Further work is necessary to investigate the biodegradation and the life cycle of these novel nanoparticles in the human body, as it has been observed that iron oxide (Fe 2 O 3 , Fe 3 O 4 ) can degrade in biological environments [20][21][22].…”

“…The T c should be independent of the applied magnetic field, as it is an intrinsic physical property of the magnetic material. For Mg 1.37 Fe 1.26 Ti 0.37 O 4 and Zn 0.54 Co 0.46 Cr 0.6 Fe 1.4 O 4 nanoparticles, this magnetic field independent behavior has been examined [11,13].…”

Structural and magnetic properties of frustrated GaxMn(3-x)O4(1.2 ≤ x ≤ 1.6) spinels

“…levels. They are promising in a wide range of applications such as multiferroic devices 1 , spintronics 2 , cathode materials with high energy densities 3 , microwaves 4 , sensors for ac and dc magnetic fields 5 , magnetic hyperthermia 6 , and magnetic refrigeration 7 . The diversity of their magnetic properties is associated with the complexity of their magnetic structure which leads to peculiar effects, such as magnetic frustration or multiferroicity.…”