MIT researchers have developed a battery-free, subcellular-sized device made of polymer designed to measure and modulate a neuron’s electrical and metabolic activity. When the device is activated by light, it can gently wrap around the neuron cell’s axons and dendrites without damaging the cells.
Scientists want to inject thousands of these tiny wireless devices into a patient’s central nervous system and then actuate them noninvasively using light. The light would penetrate the tissue and allow precise control of the devices, and thereby restore function in cases of neuronal degradation like multiple sclerosis (MS).
The MIT researchers developed these thin-film devices from a azobenzene, a soft polymer that readily reacts to light. Thin sheets of azobenzene roll into a cylinder when exposed to light, which enables them to wrap around cells. Researchers can control the direction and diameter of the rolling by changing the intensity and polarization of the light, producing a microtube with a diameter smaller than one micrometer.
Azobenzene is an insulator, which means that it can be used as a synthetic replacement for the myelin sheaths that coat axons. Myelin is an insulating layer that wraps axons and allows electrical impulses to travel efficiently between neurons. Since the body has no way of regenerating the myelin sheaths once they’re lost, the devices might help restore neuronal function in MS patients.
The device is produced by placing a drop of azobenzene onto a layer of water-soluble material. A stamp is pressed onto the drop of polymer to mold thousands of devices. The solvents are evaporated and any remaining material is gently scraped away. The final product is thousands of microscopic devices freely floating in the liquid.
The researchers tested the devices on rat neurons and found they could tightly wrap around even highly curved axons and dendrites without causing damage.
Source: Light-induced rolling of azobenzene polymer thin films for wrapping subcellular neuronal structures
https://www.nature.com/articles/s42004-024-01335-8