Magnetic particles with perpendicular anisotropy for mechanical cancer cell destruction

Abstract

We demonstrate the effectiveness of out-of-plane magnetized magnetic microdiscs for cancer treatment through mechanical cell disruption under an applied rotating magnetic field. The magnetic particles are synthetic antiferromagnets formed from a repeated motif of ultrathin CoFeB/Pt layers. In-vitro studies on glioma cells are used to compare the efficiency of the CoFeB/Pt microdiscs with Py vortex microdiscs. It is found that the CoFeB/Pt microdiscs are able to damage 62 ± 3% of cancer cells compared with 12 ± 2% after applying a 10 kOe rotating field for one minute. The torques applied by each type of particle are measured and are shown to match values predicted by a simple Stoner-Wohlfarth anisotropy model, giving maximum values of 20 fNm for the CoFeB/Pt and 75 fNm for the Py vortex particles. The symmetry of the anisotropy is argued to be more important than the magnitude of the torque in causing effective cell destruction in these experiments. This work shows how future magnetic particles can be successfully designed for applications requiring control of applied torques.

Cancer treatment by magneto-mechanical effect of particles, a review

“…This journal is © The Royal Society of Chemistry 2020 size to obtain, for instance, disk-shaped particles exhibiting magnetic vortices. 22,27,77 Finally, we observe for TMMEP various sizes and shapes of particles: from the spherical SPIONs of few nm in diameter, 44 the disk-shaped particles of few mm in diameter and few tens of nm in thickness, to the microrods of few mm in length. The sizes and shapes of the particles largely depend on the fabrication techniques, involving either bottom-up approaches (such as chemical routes, usually yielding quasi-spherical particles), or top-down approaches (such as microlithography techniques, usually yielding anisotropic particles, and allowing a wider freedom in the choice of the particles composition, size and shape).…”

“…In this approach requiring effective magnetic torque, highly anisotropic particles are oen preferred, such as for instance magnetic disks with "magnetic shape anisotropy", 24 or with "perpendicular magnetic anisotropy". 27 Subjected to the variable magnetic eld, the particle thus transfers its mechanical energy to its environment, on Fig. 1 Sketch of various types of magnetic particles exposed to variable magnetic fields, thus subjected to magneto-mechanical torques (and/or forces), tending to rotate (and/or translate) the particles.…”

“…21,29,32,41,43,44,48,51 However, in order to improve the magnetic actuation efficiency, larger magnetic susceptibilities than those of iron oxides may be required, in particular for low magnetic eld operation. Magnetic materials such as nickel, 19,33 cobalt, 27,39 or NiFe alloys, 22,27,36,55 represent good alternatives. To ensure the biocompatibility of particles composed of these toxic metals, 56 limited dissolution should be ensured, for instance via a gold coating, 57,58 or polyelectrolytes.…”

Magnetic hyperthermia with ε-Fe2O3 nanoparticles

“…Indeed, it has been suggested in the literature that cell death might also be caused by mechanical effects. [46][47][48][49][50] Moreover, there is increasing interest in using magnetic forces to activate transport through cell membranes. 51,52 Moreover the strong dependence of magnetic heating on particle mobility can be used as an advantage to heat selectively tumors with a so texture in a hard healthy tissue environment.…”

Синтез и магнитные свойства наночастиц Fe-=SUB=-3-=/SUB=-O-=SUB=-4-=/SUB=-/CoFe-=SUB=-2-=/SUB=-O-=SUB=-4-=/SUB=- со структурой ядро/оболочка

“…Эти явления часто объединяют термином " magnetic hysteresis loop tailoring", когда тщательная подборка параметров сложной магнитной системы позволяет получить настраиваемые динамические магнитные свойства [19]. Примером может служить работа [20] в которой авторам удалось получить частицы с большим откликом на внешнее магнитное поле, характеризующиеся при этом нулевой остаточной намагниченностью, что критически важно для использования их при лечении онкологических заболеваний.…”