A team of researchers from Harvard and MIT have developed polymer-based artificial vocal cords. The work, recently reported by the MIT News Office’s Anne Trafton, can help people like Julie Andrews and Steve Tyler who have damaged their vocal cords.
Indeed, the actress and singer Andrews had lost her singing voice following surgery to remove noncancerous lesions from her vocal cords. She went to Steven Zeitels, a professor of laryngeal surgery at Harvard Medical School, for help in 1997.
At the time, Zeitels was beginning to develop a new type of material that could be implanted into scarred vocal cords to restore their normal function. He soon asked Robert Langer, an expert in polymers for biomedical applications at MIT, to join him on the venture.
Trafton says the team has now developed a polymer gel that they hope to start testing in humans in a small clinical trial next year. The gel copies the essential properties of human vocal cords. It could help millions of people with voice disorders. About 6% of the U.S. population has some kind of voice disorder. Most cases involve scarring of the vocal cords.
When Langer’s lab joined forces with Zeitels’s team, they chose to work with polyethylene glycol (PEG) as the starting material. PEG was an appealing choice, in part because it is already used in many drugs and medical devices approved by the U.S. Food and Drug Administration (FDA).
By altering the structure and linkage of PEG molecules, the researchers can control the materialâ€™s viscoelasticity. In this case, they wanted to make a substance with the same viscoelasticity as human vocal cords. Viscoelasticity is critical to voice production because it allows the vocal cords to vibrate when air is expelled through the lungs.
For use in vocal cords, the researchers created and screened many variations of PEG and selected one with the right viscoelasticity, which they called PEG30. In laboratory tests, they showed that the vibration that results from blowing air on a vocal-fold model of PEG30 is very similar to that seen in human vocal folds. Also, tests showed that PEG30 can restore vibration to stiff, non-vibrating vocal folds such as those seen in human patients suffering from vocal-fold scarring.
The researchers have tested their polymer medical device on healthy dogs. The animals showed no sign of damage four months after the treatment.
According to FDA guidelines, the gel would have to be categorized as an injectable medical device. The researchers have applied for a patent and moving towards FDA approval.
If the polymer device does get approved for human use, the gel most probably will have to be injected at least once every six months, because it slowly breaks down.
Source: “New material could offer hope to those with no voice,” MIT News Office, 07/14/11
Source: “Mimicking vocal cord vibrations,” YouTube
Rajendrani "Raj" Mukhopadhyay is a science writer and editor who contributes news stories and feature articles on scientific advances to a variety of magazines. Raj holds Ph.D. in biophysics from Johns Hopkins University.