Nano-Magnets Produced by Bacteria Could Soon Target Tumors

Sarah Staniland, from the School of Biological Sciences, University of Edinburgh (Scotland, UK), and colleagues, including Dr. Andrew Harrison, who is based at the Institut Laue-Langevin (Grenoble, France). The study was published in the early online issue in March 2, 2008 in the journal Nature Nanotechnology.

Some bacteria have the ability to digest iron into tiny nanoparticles of magnetite (Fe3O4) that are enclosed in lipid vesicles or membranes. These "magnetosomes,” as they are called, have considerable potential for medical use because of their greater biocompatibility and convenient narrow and uniform shape, compared to manmade versions. Bacteria use them like tiny compasses to help them search for environments rich in oxygen.

For use in medicine, a significant advantage could be gained if the magnetic properties of magnetosomes could be controlled, for instance, by chemically doping them; but before this study, that had not been demonstrated very successfully. Dr. Staniland and colleagues showed that they could inject the magnetosomes with three types of Magnetospirillum bacteria combined with cobalt.

The presence of cobalt in the magnetosomes increases their ability to stay magnetized when they are removed from a magnetic field. Measuring the coercive field necessary to reverse their magnetization showed that the increase in magnetic field strength conferred by the cobalt was between 36-45%, depending on the type of bacteria and the amount of cobalt absorbed.

Using a range of measuring techniques such as elemental analysis, X-ray absorption, and magnetic circular dichroism (effect of magnetic field on polarized light), Dr. Staniland and colleagues estimated the cobalt content of the magnetosomes to be between 0.2 and 1.4%.

The investigators concluded that their findings "provide an important advance in designing biologically synthesized nanoparticles with useful highly tuned magnetic properties.” The researchers speculated that magnetosomes that can stay magnetized longer could one day be used to target and destroy cancer cells. They could be guided to the tumor using magnetic force, and once there, by reversing the magnetic field they could be heated up and kill the cells. Another application could be to use them to transport drugs to the precise site of the tumor. Dr. Staniland reported that "for nanoparticles to be used in medicine you need them to be a very uniform size and shape and bacteria are very good for that.”

Explaining in a recent BBC News report, Dr. Staniland stated "you would move them with a normal magnetic field and then heat them with the opposing field.” Cancer experts reported nanotechnology like this is an exciting new field that could lead to new medical treatments, but the research is still very much at an early stage.


Related Links:
University of Edinburgh
Institut Laue-Langevin