Smart gels know when to flow, when to toughen up

To help carry drugs to damaged tissue, new injectable gels flow like a liquid through a needle, but stiffen up once they're inside the body.
Written by Janet Fang, Contributor

Injectable gels would be great for carrying drugs to tissue inside the body that’s damaged. But oftentimes, gels that can be injected lose their solid structure once they’re inside.

Now, engineers have designed an injectable gel that responds to the body’s high temperature by becoming more durable, allowing it to function over a longer period of time. MIT News reports.

Shear thinning hydrogels can switch between solid and liquid states. They flow like a liquid when under mechanical stress (such as being pushed through an injection needle), but return to their normal solid-like state once inside the body.

However, they could be exposed to mechanical stresses in the body, and if they start shifting into their liquid state again, they can fall apart.

“How do you undergo a transition from not durable, which is required to be injected, to very durable, which is required for a long, useful implant life?” asks study researcher Bradley Olsen from MIT.

So his team created a reinforcing network within a gel that’s only activated when it's heated to body temperature.

A second reinforcing network takes shape when polymers that are attached at the ends bind together. At lower temps, these (soluble) polymers float freely in the gel. When heated to body temperature, they become insoluble and separate out of the watery solution – allowing them to join together and become even more durable.

The gels stay stiff and are slow to degrade – which would be useful for carrying drugs or cells to help regenerate damaged tissue. But they can also be tuned to degrade over time, which would be useful for long-term drug release.

The work was reported in Advanced Functional Materials.

[Via MIT News Office]

Image by lloydabell34 via Flickr

This post was originally published on Smartplanet.com

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