Magnetic nanoparticles are exactly what they sound like. They are particles on the nanoscale which can be affected by magnetic fields due to containing magnetic element such as iron or cobalt. Now when an alternating magnetic field is applied to the particles they have been shown to generate heat in a very efficient manner. This has led to a multitude of ideas being presented to apply this effect with the the possibility of medical uses rising above all. The idea is to use some iron oxide nanoparticles (biocompatible of course to prevent poisoning) which could be targeted to specific areas such as cancer cells. As magnetic fields are not weakened much by human flesh these particles could be given significant amounts of energy from the magnetic field resulting in localised hyperthermia to kill off the cancer.
Now of course we can’t just start sticking metallic particles into people and see what happens as there are still a number of aspects to consider. For the magnetic nanoparticles to be carried to the right place they would have to be loaded onto biological species such as liposomes. The interactions the particles make with their surroundings determine things such as the thermal dissipation and magnetic interactions. In particular the dipole-dipole (polar and therefore semi-charged bond) interactions found so often in biological systems can wreak havoc on the particles response to the magnetic field in ways that are still not understood.
In order to gain a greater understanding a model was created where the nanoparticles were seen as spherical particles of set volume and inertia carrying 100 magnetic dipoles each. These were projected as being placed in a fluid of set viscosity at 320 K. Using the concept of detailed balance, where it is assumed that every microscopic interaction is reversible even if, taken as a whole, they aren’t, it was possible to predict numerically the coupling of the nanoparticles with their surroundings. Practically, the results show that if the particles move to within a few diameters of each other then the magnetic field needs to oscillate at a much higher frequency to counteract biological interference.