Daily Times

A group of researchers at the University of Chicago, led by Francisco Benzanilla, created gold nanorods that will attach to specific molecules embedded in nerve cell membranes. A gentle pulse of infrared light warms the nanorods which in turn causes the neurons to fire. They’ve tested the system using dorsal root ganglion [DRG] neurons, which cluster in the spinal cord and are important for relaying information about pain and touch. Costandi writes:

The researchers added these particles to DRG neurons growing in Petri dishes, so that they would bind to the cells displaying the relevant proteins on their surface. They then exposed the cells to millisecond pulses of visible light, which heated up the particles, causing the cells to fire nervous impulses in response. This was possible not only in isolated neurons but also in slices of tissue from the rat hippocampus. In both situations, the particles stayed firmly in place when added in low concentrations, allowing for repeated stimulation of the cells for over half an hour.

A second group at MIT is using nano-sized iron oxide spheres that heat up when a magnetic field passes over them. They injected those particles into mice whose neurons had been primed to be sensitive to heat. Normally brain cells don’t need to sense heat, but a virus can carry the gene needed for the heat sensor up into the brain. The neurons incorporate that gene into their own genome and build the sensor. Then when the iron nanoparticles arrive and are warmed by a magnetic field, the neurons sense that and fire.