Magnetosome-inspired synthesis of soft ferrimagnetic nanoparticles for magnetic tumor targeting

Magnetic targeting is one of the most promising approaches for improving the targeting efficiency by which magnetic drug carriers are directed using external magnetic fields to reach their targets. As a natural magnetic nanoparticle (MNP) of biological origin, the magnetosome is a special "organelle" formed by biomineralization in magnetotactic bacteria (MTB) and is essential for MTB magnetic navigation to respond to geomagnetic fields. The magnetic targeting of magnetosomes, however, can be hindered by the aggregation and precipitation of magnetosomes in water and biological fluid environments due to the strong magnetic attraction between particles. In this study, we constructed a magnetosome-like nanoreactor by introducing MTB Mms6 protein into a reverse micelle system. MNPs synthesized by thermal decomposition exhibit the same crystal morphology and magnetism (high saturation magnetization and low coercivity) as natural magnetosomes but have a smaller particle size. The DSPE-mPEG-coated magnetosome-like MNPs exhibit good monodispersion, penetrating the lesion area of a tumor mouse model to achieve magnetic enrichment by an order of magnitude more than in the control groups, demonstrating great prospects for biomedical magnetic targeting applications.