Light switch inside brain: Laser controls individual nerve cells in mouse

Scientists in Freiburg and Basel, Switzerland, have developed an implant that is able to genetically modify specific nerve cells, control them with light stimuli, and measure their electrical activity all at the same time. This novel 3-in-1 tool paves the way for completely new experiments in neurobiology, also at Freiburg's new Cluster of Excellence BrainLinks-BrainTools.

Birthe Rubehn and her colleagues from the Department of Microsystems Engineering (IMTEK) and the Bernstein Center of the University of Freiburg as well as the Friedrich Miescher Institute for Biomedical Research in Basel describe the prototype of their implant in the journal Lab on a Chip. They report that initial experiments in which they implanted prototypes into mice were successful: The team was able to influence the activity of nerve cells in the brain in a controlled manner by means of laser light pulses.

The team used an innovative genetic technique that makes nerve cells change their activity by shining different colored lights on them. In optogenetics, genes from certain species of algae are inserted into the genome of another organism, for instance a mouse. The genes lead to the inclusion of light-sensitive pores for electrically charged particles into a nerve cell's membrane. These additional openings allow neuroscientists to control the cells' electrical activity.

However, only the new implant from Freiburg and Basel makes this principle actually practicable. The device, at its tip only a quarter of a millimeter wide and a tenth of a millimeter thick, was constructed on the basis of polymers, special plastics whose safety for implantation into the nervous system has been proven.

Unlike probes developed so far, it is capable of injecting substances necessary for genetic modification, emitting light for the stimulation of the nerve cells, and measuring the effect through various electrical contacts all at once. Besides optimizing the technique for production, the scientists want to develop a second version whose injection channel dissolves over time, reducing the implant's size even further.