We are all familiar with brain machine interfaces abundantly popularized in the news media. These interfaces are particularly useful for immobilized people, for example patients with Amyotrophic Lateral Sclerosis or spinal injuries. They rely on the traditional electrode implantation concept that shock neurons to induce action potentials. Electrode implantation is very invasive however, since it requires to surgically inserting 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 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 neural hybrids will contain gold nanoparticles acting as nano-antennas to trigger action potentials in response to external electromagnetic stimulation. In effect they could behave as implantable ‘bio-electrodes’ in brains or spinal cords. Beside constituting the base for new types of brain machine interfaces, nano devices present inside neurons offers untapped opportunities for producing energy within the neurons themselves.
The image above illustrates a microtubule, a cylinder-like intracellular structure abundant inside neurons and here shown loaded with gold nanorods (yellow), fast switching diodes, and other metallic nanorods, all randomly inserted inside microtubules. Some of these random arrangements may reconstitute a functional rectenna. Rectennas are a particular type of asymmetric antennas which convert the terahertz oscillating electric field of incoming near infrared light into DC electronic currents. Such currents can induce action potentials in the host neuron via membrane depolarization or alternatively supply energy to the neuron via reduction of electron acceptors NAD+, depending on the rectenna location. Near Infrared wavelength can penetrate a few centimeters below the skull, therefore external and non-invasive devices such as laser diodes, located outside the head, could stimulate nano-rectennas hosted in bioengineered neurons implanted inside the cortex. In effect, this would transform each nano-rectenna/neurons hybrid into a remotely activable electrode. Being autologous with their host, these neurons will interface normally within the host neural network via normal synapses. In spinal cord injuries where axonal tracts are interrupted by cysts and fibrotic tissues, the implantation of a small number of nano-rectennas-carrying neurons could replace surgically inserted electrodes.