Synthetic Material Revitalizes Damaged Vocal Cords

A new study describes a synthetic polymer that can mimic the viscoelastic properties of human vocal cords.

Researchers at Harvard University (Boston, MA, USA) and MIT (Cambridge, MA, USA), have been developing a modified form of polyethylene glycol 30 (PEG30) that mimics the viscoelastic properties of human vocal cords. In laboratory tests, the vibration that results from blowing air on a vocal-fold model of the synthetic PEG30 is very similar to that seen in human vocal folds. Also, tests showed that PEG30 can restore vibration to stiff, nonvibrating vocal folds such as those seen in human patients suffering from vocal-fold scarring.

The researchers then tested the biocompatibility of the gel by injecting it into the healthy vocal folds of dogs. After four months, no significant inflammation was observed on micro-laryngoscopic examination. Magnetic resonance imaging (MRI) and histologic analyses revealed time-dependent resorption of the PEG30 hydrogel by phagocytosis, with minimal tissue reaction or fibrosis. The study describing the development of PEG30, as well as other medical applications that could be achieved by modifying the chemical properties of the PEG, were published in the March 2011 issue of the Annals of Otology, Rhinology & Laryngology.

“What we did differently is we looked at this as a mechanical problem that we need to solve,” said lead author Sandeep Karajanagi, PhD, a former MIT researcher. “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.”

The researchers are now working on developing a manufacturing process that will generate enough of the material, in high quality, for human trials. They are also working on developing methods for injecting the material at the right location to treat human vocal cords. The researchers have applied for a patent on the material and are working toward US Food and Drug Administration (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.

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