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Gel turns to bone-growing scaffold when injected into the body

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May 26, 2014

A vial of the clear hydrogel turns to a white semi-solid as it's heated to body temperatur...

A vial of the clear hydrogel turns to a white semi-solid as it's heated to body temperature

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In the field of regenerative medicine, one of the current areas of interest involves the use of scaffolding-like materials that a patient's own cells can be "seeded" onto. As the cells grow and populate the material, they gradually replace it, until all that remains is a solid piece of tissue or bone. Now, scientists at Houston's Rice University have taken that concept a step further, using a polymer that is liquid at room temperature, but that solidifies into a scaffold when injected into patients' bodies.

The Rice team created a hydrogel containing a polymer known as poly(N-isopropylacrylamide), which has also recently been put forward as a "reversible glue" for temporarily sealing eye injuries while patients are in transit. As long as it's kept below body temperature, the polymer remains in a liquid state. Once heated by the body, however, it becomes a semi-solid.

The scientists envision the gel being injected into the body in areas where bone has been lost to injury or disease. As it solidifies, it will fill the void, providing a scaffold for cells from the adjacent natural bone to grow into.

The scientists added chemical cross-linkers to the gel, to keep it from shrinking as it so...

In the case of some other "thermogelling polymers," however, they expel their own water content while solidifying. This causes them to shrink to as little as one-third their original size, thus negating their whole void-filling function. The team got around that problem by adding chemical cross-linkers to the gel. These stabilize the material, keeping it from shrinking as it sets.

As an added benefit, the bonds formed by the cross-links are gradually degraded by alkaline phosphatase, which occurs in high levels when new bone is being formed. This means that as natural bone grows into the material, the material itself will disintegrate to make way for the bone. It's believed that the rate of degradation could be tweaked to allow for different bone growth rates, as they vary between individuals and different parts of the body.

A paper on the research was recently published in the journal Biomacromolecules.

Source: Rice University

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away.   All articles by Ben Coxworth
3 Comments

I can see the biggest problem - how does the doctor control the shape the gel ends up taking?

If I want a round or oval bone shape to, say, bridge a broken collarbone, what is there to stop the gel flattening out or seeping sideways into any available space before it warms up and forms the scaffold?

The Skud
26th May, 2014 @ 07:40 pm PDT

I think the next major application should be a gel to form & grow in place joint cartilage in hips, knees, & elbows. And, yes, one of the big challenges is both to shape an appropriate surface on each side of a knee joint and to do so with a laparoscopic procedure to minimize the intrusion. I hope this gets figured out before I need to have a knee or hip or whatever rebuilt!

StWils
27th May, 2014 @ 12:25 pm PDT

Would this fix teeth after amalgam removal?

Kääriäinen Heikki Haykey
29th May, 2014 @ 12:40 pm PDT
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