Many are familiar with the brain machine interfaces abundantly popularized in the news medias. These interfaces are particularly useful for immobilized people, for example patients with Amyotrophic Lateral Sclerosis or spinal injuries. Such interfaces rely on the traditional electrode concept that shock neurons to produce action potentials. The procedures are very invasive since they require the surgical implantation of electrodes near neurons, producing bleeding, scar and continuous stress in the surrounding nervous tissues.  A solution to these problems is the generation of stand-alone autologous-induced-neurons that can be reimplanted without rejection in their initial donor and deliver action potentials, remotely. Here, we propose a new concept of brain-machine interface that combines genetic engineering and nanotechnologies to generate neuron-machine hybrids that can synapse normally with other neurons. These neuron hybrids, or ‘augmented’ neurons, will contain gold nanoparticles or nanoantennas capable of triggering action potentials in response to external electromagnetic stimulation. In effect they could behave as implantable ‘bio-electrodes’ in brains or spinal cords. The principle is illustrated below.

Above is an illustration of a gold nanosphere located near the membrane channel of a neuron. When light illuminates the nanosphere, the surface electrons resonate at a particular frequency. Light is scattered, and the nanoparticle releases energy in the form of heat. This heat in turn can trigger the opening of the channel that let extracellular ions enter the intracellular space and depolarize the neuron. This depolarization induces the generation of an action potential which can propagate along the axon and stimulate other neurons through synapses. Other interesting effects can be obtained with light. Illuminated nanoparticles generate strong electric fields that can activate membrane channels and induce neurons to fire up, and integrating nano devices with existing subcellular structures even offers additional opportunities.

The image below illustrates a microtubule, a cylinder-like subcellular structure inside neurons. Here, the microtubule is loaded with gold nanorods, which are nanoparticles that can strongly absorb near infrared light. Microtubules are made of polar subunits and were suggested to behave as rectenna, producing local currents in response to electromagnetic field. Inserted nanodevices could take advantage of these properties and augment the microtubules light gathering at near infrared. This wavelength can reach several centimeters inside the brain cortex, therefore external and non-invasive devices such as laser diodes, located outside the head, could stimulate bioengineered neurons that were implanted deep inside the cortex. In effect, this would transform each implanted neuron into one electrode remotely activable. One single implanted neuron, being autologous with its host, should integrate normally the neural network and stimulate thousands of other neurons via normal synapses. In turn, the implantation of a million augmented neurons should generate an astonishing increase in global neural interconnectivity, several orders of magnitude higher than what can be achieved with a traditional electrode concept.