Orientation of magnetic nanoparticles used for cancer treatment compared to ordinary magnets. The illustrations show (a) the needle of a magnetic compass oriented in the direction of the Earth’s magnetic field, and (b) magnetic nanoparticles aligned perpendicular to the magnetic field. ©National Institute of Materials Science (NIMS)

Research at the National Institute for Materials Science (NIMS) in Japan has provided a detailed insight into the mechanisms of heat generation in magnetic nanoparticles that could be used to kill cancerous cells.

Magnetic thermotherapy is one of the newest potential cancer treatments. It works by delivering tiny nano-sized magnets (magnetic nanoparticles) to cancer cells using drug delivery techniques. Once there, they are exposed to an alternating magnetic field which causes them to heat up, and that overheats and kills malignant cells. There are virtually no side effects, and researchers are eager to develop the technique for practical use as soon as possible.

There are, however, major obstacles to progress, because of inconsistencies between theoretical predictions of the amount of heat magnetic particles generate, and experimental results. Scientists accept the mechanisms involved need to be understood in more detail before the design of magnetic particles for practical use can be optimised.

Previously, the behaviour of nanoparticles had always been calculated according to the energy produced by their stationery magnetic field. But now, Dr Hiroaki Mamiya and colleagues at NIMS’s Quantum Beam Unit have carried out a simulation under near-actual conditions, taking into account the large amount of heat that is dissipated into the surrounding cancerous tissue.

They found that the orientation of the magnetic nanoparticles changes dramatically depending on the size and shape of the nanoparticles themselves, the viscosity of their surroundings, and the properties of the alternating magnetic field they are exposed to. Under certain conditions, the nanoparticles align in planes perpendicular to the magnetic field. This happens when the magnetic field has a high frequency and comparatively weak in amplitude. The team also revealed that the heat generation properties of the magnetic nanoparticles are influenced by their orientation.

These conclusions represent a big step forward in the field. Once they are verified in-situ, it will be possible to optimise the nanoparticles for the treatment of different cancers.

For further information contact:

Dr Hiroaki Mamiya
Quantum Beam Unit
National Institute for Materials Science, Japan