Biodegradable Sponge Supports Bone Regrowth

A newly engineered, malleable material may replace grafting for sufferers of bone loss

The healing process can often hit a wall when significant bone loss, as from cancer removal or lesions, occurs. However, a new sponge-like material developed by biomedical engineers and researchers at Texas A&M; may offer a revolutionary way to fill the treatment gap.

The newly developed “bone foam” is made out of a polycaprolactone, a polymer already used to separate healing tissues, and can construct a sort of scaffold around and between healing bones to let cells regrow themselves. As the American Chemical Society has reported, the “self-fitting” material expands in warm salt water to perfectly fill bone gaps and support healing.

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Project leader Melissa Grunlan, PhD. presented the team’s findings at the ACS’s annual meeting in San Francisco on August 13th. As Wired explains, Grunlan stressed the qualities of the materials that make it uniquely applicable for bone regrowth: firstly, that it becomes malleable at 140° F or above, but stiffens at body temperature, allowing a surgeon to shape the material to fit a bone lesion before it cools and “locks” into place; secondly, that it breaks down slowly and safely inside the body.

Most important to their achievement, however, was their choice to combine these elements in a stiff but porous material; “after the foam is in place, bone cells [can] come in and replace the foam, which is absorbed into the body and naturally excreted,” Grunlan explains.

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Current treatments include bone filling and bone grafting (pictured below), both of which present numerous problems for surgeons and patients alike. “The problem is that the autograft is a rigid material that is very difficult to shape into these irregular defects,” Grunlan tells the ACS. She also explains that harvesting bone for the autograft can itself create complications at the source from which the bone was taken. Today’s bone filling methods involve using bone putty or cement to plug gaps. However, these materials become extremely brittle when they harden, and lack the porousness of Grunlan’s proposed sponge filler, which allows new bone cells to amass and regrow tissue. Notably, both methods seem to lack the subtlety required to reconstruct, for example, a person’s facial features and general appearance after cranio-maxillofacial bone loss or from birth defects.

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The team’s research to date has been limited to seeding osteoblasts — cells which synthesize bone — in samples of the sponges, but with encouraging results. The next step, Grunlan said, will be to test the ability of the material’s shape memory polymers to heal cranio-maxillofacial defects in animals. “The work we’ve done in vitro is very encouraging,” she says. “Now we’d like to move this into preclinical and, hopefully, clinical studies.”

[h/t] Gizmodo

Images: Elsevier Ltd., Grunlan Research Group

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