Slippery material for lubricating joints inspired by nature

Date: Aug-19-2014 For some time, scientists have been aware that synovial fluid in joints contains a

natural substance that helps keep them well lubricated. Now, by mimicking its properties,

engineers at Johns Hopkins University in Baltimore, MD, hope to develop a new material that

delivers long-lasting lubrication in artificial joints, and other specific spots in the body

where surfaces move against each other.

"What I like about this concept is that we're mimicking natural functions that are lost using synthetic materials," says Prof. Elisseeff.

The team writes about the new material, and the potential it offers, in the journal Nature

Materials. As well as helping to ease joint pain, other areas of possible use include making contact lenses more comfortable.

The molecule they are investigating is called hyaluronic acid (HA), which exists in several

forms in the body where lubrication is needed.

One form of HA reduces inflammation and protects cells from metabolic damage. In the body, HA

is bound to the surfaces it protects by a protein. Research shows that in damaged, diseased and

aging knees, hips, shoulders and elbows, this protein is no longer able to hold onto HA.

Viscosupplementation is a popular treatment for painful joints and consists of injecting HA

into the painful joint. However, if the cause of the pain is the lack of the protein that helps

bind HA to the affected surface, then it does not offer long-lasting benefit.

The injected HA is soon washed away by the body's natural cleaning processes.

'Chemical handle' holds HA in place

Thus, led by Jennifer H. Elisseeff, a professor at the Wilmer Eye Institute at Johns Hopkins,

the team sought to find a way to keep HA in place. They found their answer in molecules known as

HA-binding peptides (HABpeps).

The scientists used HABpep as a "chemical handle" to attach HA onto natural and artificial

surfaces with the help of another synthetic molecule, polyethylene glycol.

In the lab, they tested the new material in cultured tissue and joint and eye surface

tissue in live animals. They found the bound HA did not wash away easily, and it reduced friction

as well as when the tissues were immersed in a bath of HA:

"Tissue surfaces treated with the HA-binding system exhibited higher lubricity values, and in

vivo were able to retain HA in the articular joint and to bind ocular tissue surfaces," they

note.

HABpep holds HA in place 12 times longer

In another set of experiments, they also tested an HABpep designed to attach to cartilage. They

injected rats' knees first with some HABpep, then with some HA, and found the HA stayed in place

12 times longer than it did in rats that had received only HA injections without HABpep.

The team suggests this shows HABpeps may be a useful addition to viscosupplementation by

helping the HA to stay in place longer. They also conclude:

"Biomaterials-mediated strategies that locally bind and concentrate HA could provide physical

and biological benefits when used to treat tissue-lubricating dysfunction and to coat medical

devices."

Although it will be some time before such a material is ready for use in humans, the team

highlights that theirs is yet another example of where nature has inspired the solution to a

medical problem.

Prof. Elisseeff, who is also of the Johns Hopkins University departments of Biomedical

Engineering and of Materials Science and Engineering, says:

"What I like about this concept is that we're mimicking natural functions that are lost using

synthetic materials."

Meanwhile in November 2013, Medical News Today learned how another team of

researchers - also inspired by nature - is refining sea coral for use in bone

grafts.

Written by Catharine Paddock PhD

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Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.