Exposure to magnetic field (MF) is one of the oldest instruments in biomedical practice along with the use of chemical, thermal and mechanochemical tools or approaches. However, in comparison to the latter ones, it has much more limited physical background so that its impact is much less predictable and reliable. As a result, its applications are scarce currently. This paper briefly discusses three main directions of the MF application in biomedicine in the past, nowadays and in the future.
The first one is the exposure to steady or low frequency (f<300 Hz) non-heating MF. It is the oldest but still the most controversial and the least reliable approach. There is no universally accepted theory or even mechanisms of its impact on biological objects. The second one is the use of radio frequency (f ~ 10-100 MHz) MF for heating biologic materials or objects due to eddy currents or dielectric losses. The influence of the MF itself in this approach appears to be negligible or insignificant.
And the third approach employs magnetic nanoparticles (MNP) introduced into the object beforehand or existing there naturally as a mediators and enhancers of MF action on biomolecular structures. Depending upon MF characteristics, heating (at f = 100-800 kHz) or magnetomechanical activation (at f < 1 kHz) within the region of interest can be implemented. In the latter case, the heating is negligible and the impact is due to the nanomechanical activation of biomolecular structures localized within the region close in size to MNP, i.e. within several tens of nanometers. Such nanomechanical activation can affect target cell functioning or induce its apoptosis.
Comparison of requirements and outcomes of these 3 approaches is presented, and advantages, drawbacks, uncertainties and risks of each of these approaches are analyzed.