|The polymer foam scaffold has interconnected pores that|
allow bone cells to migrate into the area and begin
healing damaged tissue.
A research group has created a polymer foam that is malleable after treating with warm saline, allowing it to precisely fill a bone defect before hardening into a porous, sponge-like scaffold that promotes new bone formation. The research was published in the journal Acta Biomaterialia. The team envisions the material as a treatment for cranio-maxillofacial bone defects, gaps in bone occurring in the head, face or jaw areas. These defects, which can dramatically alter a person's appearance, can be caused by injuries, birth defects such as cleft palates or surgical procedures such as the removal of tumors.
In order to repair these defects, the polymer foam developed by the team acts as a scaffold, a temporary structure that supports the damaged area while promoting healing by allowing bone cells to migrate into the area and repair the damage tissue. Ultimately, the scaffold dissolves, leaving behind new bone tissue.
Key to the material is its malleability after brief exposure to warm saline (140 degrees Fahrenheit), allowing surgeons to easily mold the material to fill irregularly shaped gaps in bone. Once a defect is filled, the material cools to body temperature and resumes its stiff texture, locking itself in place. This self-fitting aspect of the material gives it a significant edge over autografting, the most common treatment for these types of bone defects. Autografting involves harvesting bone from elsewhere in the body, such as the hip, and then arduously shaping it to fit the bone defect. In addition to its obvious limited availability, the bone harvested through autografting is very rigid, making it difficult to shape and resulting in a lack of contact between the graft and the surrounding tissue. When this occurs, complications can arise. For example, a graft can inadvertently dissolve through a process known as graft resorption, leaving behind the defect.
Another therapy involves filling the defect with bone putty, but that material can be brittle once it hardens, and it lacks the pores necessary for bone cells to move into the area and repair the tissue. By tweaking the polymer scaffold through a chemical process that bonds individual molecular chains, the research team overcame that issue and produced a sponge-like material with interconnected pores. They also coated the material with a bioactive substance that helps lock it into place by inducing formation of a mineral that is found in bone. The coating help osteoblasts, the cells that produce bone, to adhere and spread throughout the polymer scaffold. Think of it as a sort of "boost" to the material's healing properties.
Thus far, the results have been promising; after only three days the coated material had grown about five times more osteoblasts than uncoated versions of the same material. In addition, the osteoblasts present within the scaffold produced more of the proteins critical for new bone formation. The team plans to continue studying the material's ability to heal cranio-maxillofacial bone defects by moving testing into preclinical and clinical studies.