Remote Controlling Brain Activity Through Nano Particles Of Gold

The blood brain barrier (BBB) controls the brain microenvironment and limits penetration of the central nervous system (CNS) by chemicals, thus creating an obstacle to many medical imaging and treatment procedures. Research efforts to identify viable routes of BBB penetration have focused on structures such as micelles, polymeric nanoparticles and liposomes as drug carriers, however, many of them failed to provide unequivocal proof of BBB penetration. Here we proved that gold nanoparticles (AuNPs) penetrate the BBB in rats to reach brain regions.

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. 

Injection of AuNPs to the abdominal cavity of rats resulted in levels of gold found in blood, urine, brain regions and body organs. After perfusion the concentration of gold in brain regions diminished dramatically indicating that most of the gold was in venous blood and not in the brain tissues. Injection of Na, K or Ca ion channel blockers reduced BBB penetration by half. A biological half-life of 12.9 ± 4.9 h was found for the gold nanoparticles. Possible mechanisms for the transport of AuNPs through the BBB are discussed.

BBB penetration by AuNPs is spontaneous without the application of an external field. A major amount of gold resides in blood vessels therefore perfusion required. Ion channel blockers can be used to control the transport of AuNPs.

The treatments are still far from remote-controlling anyone’s brain, but they do demonstrate some of the innovative ways scientists are thinking about nanotechnology and medicine.