A lubricant that doesn’t wash away could ease arthritis pain in knees and shoulders, keep artificial joints working smoothly, and even make contact lenses more comfortable.
Biomedical engineers discovered a way to bind the lubricant to a sticky man-made molecule that then essentially locks it in place on the surface of cartilage and eye tissues.
“What I like about this concept is that we’re mimicking natural functions that are lost, using synthetic materials,”
says Jennifer H. Elisseeff, professor of ophthalmology, biomedical engineering, and materials science at Johns Hopkins University.
Scientists have long known that hyaluronic acid (HA) is abundant in the fluid that surrounds joints like knees, shoulders, and wrists.
HA is an important component for naturally lubricating tissues; one form of the biochemical also reduces inflammation and protects cells from metabolic damage.
Diseased, damaged, or aging joints in hips, knees, shoulders, and elbows often have far lower concentrations of HA, presumably because a protein that binds HA molecules to joint surfaces is no longer able to retain HA where it is needed.
HA injections, a method known as viscosupplementation, have become popular treatments for painful joints. Without a way to retain HA at the site, however, the body’s natural cleaning processes soon wash it away.
For the new study, Elisseeff looked at molecules known as HA-binding peptides (HABpeps), which stick to HA.
In the laboratory, using HABpep as a chemical handle, she and her colleagues used a second, synthetic molecule, polyethylene glycol, to tie HA onto surfaces that included natural and artificial cartilage and eye tissue.
Tests on tissues and in animals show that the bound HA didn’t easily wash away. It also reduced friction as successfully as when the tissues were immersed in a bath of unbound HA.
When researchers injected a HABpep designed to attach to cartilage in rat knees, then injected HA, that HA stuck around 12 times as long as it did in rats that hadn’t been given HABpep, suggesting that these peptides could be a promising addition to viscosupplementation.
The HABpep-polymer system could also be useful as an eye-drop solution to improve contact lens comfort and keep damaged eye tissues lubricated.
Anirudha Singh, Michael Corvelli, Shimon A. Unterman, Kevin A. Wepasnick, Peter McDonnell & Jennifer H. Elisseeff
Enhanced lubrication on tissue and biomaterial surfaces through peptide-mediated binding of hyaluronic acid
Nature Materials 13, 988–995 (2014) doi:10.1038/nmat4048
Photo: David Goehring/Flickr