Hydrogel transforms into solid bone-healing material upon exposure to light

Missing portions of bone, whether due to injury, disease, or other causes, can be challenging to replace. However, a new injectable hydrogel has the potential to change this by turning into a robust bone regeneration material when exposed to visible light.

While fractures usually heal on their own, large bone deficits often do not regenerate naturally. This requires harvesting bone tissue from another part of the patient’s body, which is invasive and painful.

To address this issue, researchers are developing bone-like porous materials that can be placed in the bone deficit. Cells from nearby bone tissue migrate into the material, allowing them to reproduce as the material breaks down and gets replaced by natural bone.

Some experimental bone regeneration materials are 3D-printed outside the body and secured into the deficit using adhesive, but this method can sometimes fail. Another approach involves injecting the material directly into the deficit as a gel that hardens into a solid. However, some substances take a long time to set, are not biodegradable enough, or lack mechanical strength.

This is where the new hydrogel material comes in. Developed by Prof. Hyung Joon Cha and colleagues at Korea’s Pohang University of Science and Technology (POSTECH), the hydrogel consists of alginate, bioengineered mussel adhesive protein, calcium ions, phosphonodiol, and a photoreactive agent. When exposed to visible light, the gel crosslinks its polymer chains to become a strong, porous, biodegradable solid that bonds with adjacent bone tissue securely.

Simultaneously, amorphous calcium phosphate forms within the material, creating a bone-like compound that supports the migration and reproduction of adjacent bone cells, leading to the replacement of the material with real bone.