Whether caused by intubation during surgery, laryngeal cancer, lesion removal, or simply overuse, vocal cord scarring can limit or even eliminate some peoples' ability to speak. This is because the scar tissue is stiff, and doesn't allow the vocal cords to vibrate adequately. Some doctors have tried to soften the tissue using materials from the fields of plastic surgery and dermatology, but the treatment doesn't work in all cases, and the effects are said not to last very long. Researchers from the Massachusetts Institute of Technology (MIT) and Harvard Medical School, however, are developing a new approach - an injectable gel that mimics vocal cord tissue.
The gel was created by a team led by Steven Zeitels, a professor of laryngeal surgery at Harvard, and Prof. Robert Langer, from MIT's Department of Chemical Engineering.
They started with polyethylene glycol (PEG) gel, partly because it is already approved for use in drugs and medical devices. In order to match its viscoelasticity to that of human vocal cords, they manipulated the structure and linkage of its molecules, creating many variations of PEG in the process. The one that ended up meeting their approval, PEG30, has been shown to closely match the vibrations exhibited by vocal cord tissue, when subjected to blowing air.
Lab tests have also shown that it can restore vibration to stiffened, scarred vocal cords. The MIT/Harvard project is attempting to restore vocal functions despite the presence of scar tissue, while other approaches (such as those involving drug treatments) have focused more on trying to get rid of that tissue.
PEG30 does unfortunately break down, so the gel would likely have to be reinjected into patients' vocal cords at least once every six months. The team is now working on a method of producing sufficient quantities of the material, to facilitate a ten-patient human trial next year. They state that different versions of PEG could conceivably be designed down the road, to address other medical problems.
The video below shows how the gel performs, as compared to actual vocal cords.