Last year saw a new twist on optogenetics (see 鈥�Mind controls: Putting a light switch in the brain鈥�): magnetogenetics, or using a magnetic field to trigger the firing of genetically engineered neurons.
Arnd Pralle鈥檚 group at the State University of New York at Buffalo engineered neurons from the nematode, worm, Caenorhabditis elegans, to manufacture an ion channel that triggers electrical firing following a small rise in temperature. The neurons are heated with iron nanoparticles, which gently warm up in a magnetic field.
To test their idea, the team used the worm鈥檚 instinctive reaction to back away from a heat source. They made the the worm鈥檚 sensory neurons in the tip of its 鈥渉ead鈥� manufacture the ion channel, and chemically altered the nanoparticles so they became concentrated in the mucus protecting the worm鈥檚 head.
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When a magnetic field was turned on, the nanoparticles slowly warmed up, thus triggering electrical impulses in the neurons (). 鈥淥nce we switch on the field, most of the ,鈥� says Pralle. 鈥淲e could make them go back and forth.鈥�
The technique could be used on larger animals by injecting the nanoparticles into the blood, says Pralle, as they are small enough to diffuse into the brain. The team is now testing the technique in genetically modified mice.
The advantage of magnetogenetics over optogenetics is that unlike visible light, a magnetic field can pass through the skull, removing the need to implant optical fibres in the brain. 鈥淭his will allow us to penetrate much deeper into tissue,鈥� says Pralle.
On the other hand, optogenetics gives finer control over neuronal firing. The light source can be turned on and off almost instantaneously, while nanoparticles take several seconds to warm up. Pralle, however, predicts the process will get faster as the technique is honed.
VERDICT Still very much in the research stage; has pros and cons compared with optogenetics.
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