New Polymeric Material for Tissue Engineering

Metals and plastics can replace damaged bones in a human body, such as in hips, but what about disfigured soft, delicate tissue, like cheeks? As Kenrick Vezina reports in Technology Review, a new polymer-based biomaterial may help surgeons reconstruct soft structures which have been traditionally hard to replace, especially in the face.

The material can be injected under the skin as a liquid, massaged into shape, and then set in place by light exposure. If the material gets approved by federal agencies to get used in humans in the future, it could help patients with disfigured faces because features like cheeks and lips are challenging to surgically replace.

As Vezina explains:

Alexander Hillel and his colleagues at Johns Hopkins University have created a new type of transplant material that addresses these problems. It’s a blend of hyaluronic acid — a biological material already used as a soft-tissue implant — and polyethylene glycol, a synthetic material. The blend is a liquid polymer that can be injected — thus avoiding the need for surgery. Once injected, the material can be sculpted into the necessary shape. When exposed to light of specific wavelengths, the messy tangle of polymer chains in the liquid implant rearrange into a stable, crosshatched form, stiffening the implant.

Light in the visible range works to set the new polymer material. It’s an important detail because visible light is much safer on the skin than, say, UV light, which can damage DNA and cause cell death.

The researchers created a green-light LED array that was able to go through up to four millimeters into the skin. The polymer material set within two minutes of light exposure. Most importantly, there were no painful side effects to the light exposure.

Hillel and colleagues, who were led by Jennifer, reported in their research paper that they first tested the material in rats, trying out several ratios of Hyaluronic acid & polyethlene glycol. They were interested in seeing how long the different blends lasted because they had varying elasticities and durabilities. The implants that lasted the longest were around for almost 500 days, which means the implants may have to be reinserted annually or so.

By having different blends of the material, clinicians can have options to chose from depending on what they need for a particular surgery. Carol Stanier of Chemistry World also wote about the team’s work with the novel polymeric material. She says:

Elisseeff notes that ‘these materials can respond differently depending on where they are in the body’, so having different functional combinations is important. The team hope to help those with traumatic injuries, such as soldiers.

The researchers carried out a tiny clinical study in Canada where they injected small amounts of the material into the stomachs of three patients scheduled for tummy tucks. The implants lasted 12 weeks or so with some side effects. The researchers will do a full-scale trial next and figure out ways to overcome the side effects.

Venzina writes:

Melissa Knothe Tate, a professor in Case Western University’s Department of Biomedical Engineering, is optimistic. ‘Getting functional tissue in the right place at the right time has been a major hurdle in the field of tissue engineering,’ she says. She adds that this and other recently published technologies could indicate ‘a new age of regenerative medicine, mimicking the body’s capacity to build new tissue.’