Magnetic Nanoparticles extracted from magnetotactic bacteria as contrast agents for MRI

Biological and biomedical applications of chemically synthesized magnetic nanoparticles have often been hampered by biocompatibility problems. Naturally occurring iron-oxide nanoparticles, namely Magnetosomes (MNs), are here proposed as theranostic agents for imaging and thermotherapy of tumors. The target audience for this work is represented by basic researchers working in the field of contrast agents for MRI, molecular imaging and tumor thermotherapy.Magnetotactic bacteria (MTB) form MNs: specialized organelles that consist in membrane-enveloped and nano-sized crystals of magnetite (Fe3O4). Inside bacteria, individual MNs are organized in chains that are used by bacteria as a compass for geomagnetic navigation. Interestingly, the first description of MTB appeared in 1963 in a publication of the Istituto di Microbiologia of the University of Pavia by Salvatore Bellini; a more complete report was later published in Science1. It has been reported that MNs extracted from MTB could act as theranostic agents: as magnetic fluids for r.f. magneto-thermotherapy and, at the same time, as contrast agent for MRI. We report here the thermal and MRI contrast proprieties of MNs extracted from Magnetospirillum gryphiswaldense strain MSR-1.