Recent advances in magnetic targeting based on high magnetic field and magnetic particles

In the past few decades, the multifunctional magnetic drug carrier based on the magnetic nanoparticles and high magnetic field has been intensively researched. The magnetic drug carrier can be targeted to the tumour area not only by the chemical protocol but also by the physical one (external field). In this review, the authors first briefly discuss the fabrication process of magnetic drug carriers, which includes the synthesis of magnetic nanoparticles, fabrication of magnetic drug carriers and conjugation of anti-tumour agents. Then different targeted protocols have been summarised, including passive targeting, biochemical active targeting and biophysical active targeting namely magnetic targeting (MT). Multiple MT results both in vitro and in vivo are introduced, in which two unconventional cases are emphasised and described. The first MT clinical research with 14 peoples was performed in the last century. A 0.5-0.8 T permanent magnet was attached to the tumour area when magnetic particles conjugated with epirubicin were injected. The side effect of epirubicin had been decreased, and the four patients showed the decreasing of a tumour which proved the feasibility of MT. Different from other targeting protocols, MT needs an extra external magnetic field. So various types of MT instruments have been shown in the final part of this review, including a single strong magnetic field, homemade electronic solenoid coil assay and commercial magnetic resonance imaging.