Researchers at MIT and MGH have developed a polymer gel that mimics the vibrations of human vocal cords.
CAMBRIDGE, US: In 1997, the actress and singer Julie Andrews lost her singing voice following surgery to remove noncancerous lesions from her vocal cords. She came to Steven Zeitels, a Professor of laryngeal surgery at Harvard Medical School, for help.
Zeitels was already starting to develop a new type of material that could be implanted into scarred vocal cords to restore their normal function. In 2002, he enlisted the help of MIT’s Robert Langer, the David H Koch Institute Professor in the Department of Chemical Engineering, an expert in developing polymers for biomedical applications.
The team led by Langer and Zeitels has now developed a polymer gel that they hope to start testing in a small clinical trial next year. The gel, which mimics key traits of human vocal cords, could help millions of people with voice disorders.
About 6 per cent of the US population has some kind of voice disorder and the majority of those cases involve scarring of the vocal cords, said Sandeep Karajanagi, a former MIT Researcher who developed the gel while working as a postdoc in the Langer lab.
Some doctors treat vocal-fold scars with materials normally used in dermatology or plastic surgery, in hopes of softening the vocal cords, but those don’t work for everyone and the effects don’t last long, said Nathan Welham, Assistant Professor of otolaryngology at the University of Wisconsin School of Medicine.
Researchers have tried developing drugs that would dissolve the scar tissue, but the MIT/Harvard team decided on a different approach.
“What we did differently is we looked at this as a mechanical problem that we need to solve. We said, “Let’s not look at the scar itself as a problem, let’s think of how we can improve the voice despite the presence of the scar tissue,” said Karajanagi, who is now an instructor of surgery at Harvard Medical School and a researcher at the Centre for Laryngeal Surgery and Voice Rehabilitation at Massachusetts General Hospital.
The team chose polyethylene glycol (PEG) as its starting material. By altering the structure and linkage of PEG molecules, the researchers can control the material’s viscoelasticity. For use in vocal cords, the team called the material as PEG30.
Under FDA guidelines, the gel would be classified as an injectable medical device, rather than a drug. The researchers, have applied for a patent on the material and are working toward FDA approval. If approved for human use, the gel would likely have to be injected at least once every six months, because it eventually breaks down.
In a study recently published in the Annals of Otology, Rhinology & Laryngology, the researchers tested the biocompatibility of the gel by injecting it into the healthy vocal folds of dogs. After four months, the treated dogs showed no damage to their vocal cords.
The researchers are now working on developing a manufacturing process that will generate enough of the material, in high quality, for human trials. They hope to run a trial of about 10 patients next year.
“We think of what we do as ‘designer polymers’,” Langer said. “We can modify them depending on the problem we’re trying to solve.”
The project is funded by the Institute of Laryngology and Voice Restoration. Julie Andrews is the foundation’s honorary chairwoman.
(C) Massachusetts Institute of Technology News