A new composite material that integrates seamlessly into living tissue could someday bind bones and tendons together following an injury. A synthetic mixture of ceramic dust and a polymer can be quickly 3-D printed in an endless variety of shapes and sizes, perfect for molding it to different body parts. Its sturdy yet porous structure allows living tissues to gradually infiltrate the graft and rebuild organic structures. It is also compressible when printed in the form of a grid, allowing surgeons to mold the shape of the material to better fit the graft site.
A Better Bone
The material, called "hyperelastic bone," was created by researchers at Northwestern University as a better means of holding together or replacing broken bones. Previous materials used at graft sites were either toxic, difficult to work with or too dense for tissues to permeate them, forestalling a full recovery. The researchers say that their hyperelastic bone overcomes all of these issues, based on preliminary tests in animals. The material has not yet been tested in humans. They published their research Wednesday in the journal Science Translational Medicine. The researchers first tested their material in a mouse by fusing two of its vertebrae together. They surrounded the spine with their graft material on both sides, and after eight weeks enough bone and tissue had grown into the synthetic matrix to fuse the vertebrae together. Their next test was in a rhesus macaque with a damaged skull. They removed the weakened portion of the skull and replaced the bone with their synthetic graft. After four weeks, the graft had grown into the surrounding bone and integrated with the skull.
Strong and Flexible
The researchers print their hyperelastic bone as a thin grid-like sheet. The empty spaces give the material the ability to be rolled, pulled and squished without breaking or tearing — it pops right back into shape afterwards while retaining its strength. This is an important quality for surgeons who may need to manipulate the graft to better conform to an injury. While the hyperelastic bone has not been tested in humans, the researchers did manage to grow human stem cells on the graft in the lab, a promising sign for future tests. The material could also be used to coat foreign objects like screws used in surgery to help them better integrate into the body.