Damage to the peripheral nervous system that connects the brain and spinal cord to other parts of the body can lead to disabilities, including paralysis, numbness and chronic pain. Although peripheral nerves can regenerate, it is a slow process with limited success.
One of the solutions for the treatment of damaged nerves is electrical stimulation, the effectiveness of which has been demonstrated in many research studies. The problem is that this method usually involves performing an invasive procedure that can damage the body’s tissues.
Now, a new material developed in a joint study between the Technion-Israel Institute of Technology in Haifa and the University of Chicago paves the way for the restoration of damaged nerve tissue and heart pacing through an external light source on the body. The new development could eliminate the need for electrode transplantation.
How does it work?
Near-infrared light projected into the body hits a membrane composed of the new material that will then photo-activate the damaged nerve tissue or heart. The peer-reviewed study, entitled “Porosity-based heterojunctions enable leadless optoelectronic modulation of tissues” and published in Nature Materials, was led by Assistant Prof. Menahem “Hemi” Rotenberg of the Technion’s Faculty of Biomedical Engineering and Prof. Bozhi Tian of the University of Chicago.
The researchers created a new semiconductor device in a flexible, ultrathin membrane configuration that interfaces well with biological tissues. The idea is to use this membrane to wrap the damaged nerve tissue, or in the case of heart pacing, wrap the heart itself. This step will be carried out as part of the surgery that is necessary in any case if there is such damage.
“Our development is a photovoltaic material that converts light energy into electrical energy that affects nerve tissue,” Rotenberg said.
“In the article, we demonstrated the efficacy of the new substance in two different contexts – heart pacing and the activation of the peripheral nervous system,” he said.
“In the context of heart treatments, for example, the use of such a device can allow temporary cardiac pacing for postoperative rehabilitation and avoid the use of a temporary electrode to be inserted into the heart,” said Rotenberg, the lead author. “Because the membrane we developed is made of a silicon-based material that absorbs in the body without any toxic effect, there is no need for further surgical action to remove it from the body.”
The new material is a “therapeutic window” that allows the medical team to have an external impact on the tissues of the patient’s body, he said.
The uniqueness of the material the team developed is in its formation of a semiconducting diode junction from a single type of silicon. A diode is a two-terminal electronic component that conducts current primarily in one direction. This characteristic is highly unusual, as diodes are usually made by interfacing two types of silicon.
Semiconductors are based on energetic gaps that determine their level of conductivity. They usually consist of n-type (negatively charged) materials, which contribute an electron to the material, and p-type (positively charged) materials, which take an electron from the material and leave a hole instead. The connection between the two materials creates an efficient interface called a p-n junction, which is the building block of electronic devices and solar cells.
Because the membrane we developed is made of a silicon-based material that absorbs in the body without any toxic effect, there is no need for further surgical action to remove it from the body.
Prof. Menahem Rotenberg
The connection between the two different materials is a very complex technological challenge, so the discovery is very important because a diode is made only of p-type silicon, and the junction is built of ordinary silicon and porous silicon.
The new material was created serendipitously, Rotenberg said.
“I accidentally used a metal tweezer in the laboratory that provided iron ions to the solution – something I did not plan to happen,” he said. “The iron ions turned out to catalyze the creation of nanopores on the surface of silicon.”
The development may be useful outside of medicine
Beyond the medical field, the new development is expected to contribute significantly to various applications, including in the field of renewable energy. Since renewable energy sources such as the sun are volatile and do not operate at constant intensity throughout the day, energy storage becomes a major challenge in promoting their use.
One of the new trends is the production of hydrogen via the decomposition of water with solar radiation, because the hydrogen produced is a storable energy source. Rotenberg hopes the new material he developed with his colleagues will speed up the development of more advanced and efficient solar devices.