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A new study by scientists in the UK and France has shown it is possible to fine tune the magnetic properties of tiny "nano" magnets made by bacteria, and this technology could one day be developed to target cancer tumours.

The study is the work of Dr Sarah Staniland of the School of Biological Sciences, University of Edinburgh, and colleagues, including Dr Andrew Harrison who is based at the The Institut Laue-Langevin in Grenoble, and is published in the early online issue of 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 until this study, that had not been demonstrated very successfully.

Staniland and colleagues showed they could dope the magnetosomes of three types of Magnetospirillum bacteria with cobalt.

The presence of cobalt in the magnetosomes increases their ability to stay magnetised when they are removed from a magnetic field. Measuring the coercive field necessary to reverse their magnetisation showed that the increase in magnetic field strength conferred by the cobalt was between 36 and 45 per cent, 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 (this looks at the effect of magnetic field on polarized light), Staniland and colleagues estimated the cobalt content of the magnetosomes to be between 0.2 and 1.4 per cent.

They 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 magnetised longer could one day be used to target and destroy cancer cells, reported BBC News.

They could be guided to the tumour 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 tumour.

Staniland told the media 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."

"You would move them with a normal magnetic field and then heat them with the opposing field," she explained in the BBC News report.

Cancer experts say 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.

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