By blending pulverized natural bone with man-made plastic, researchers at The Johns Hopkins University 3D-printed replacement skeletal structures of the head and face, including the lower jaw of a female patient. The team's composite material combines the strength and printability of plastic with the biological “information” contained in natural bone.
The researchers began with polycaprolactone, or PCL, a biodegradable polyester used in making polyurethane. PCL's lower melting point -- 80 to 100 degrees Celsius -- worked well with the sensitive biological materials that suffer damage under high temperatures.
The polyester was mixed with increasing amounts of “bone powder,” made by pulverizing the porous bone inside cow knees after stripping it of cells.
“Bone powder contains structural proteins native to the body plus pro-bone growth factors that help immature stem cells mature into bone cells,” said Warren Grayson, Ph.D., associate professor of biomedical engineering at the Johns Hopkins University School of Medicine. “It also adds roughness to the PCL, which helps the cells grip and reinforces the message of the growth factors.”
To test whether the scaffolds encouraged bone formation, the researchers added human fat-derived stem cells -- taken during a liposuction procedure -- to scaffolds immersed in a nutritional broth lacking pro-bone ingredients.
After three weeks, cells grown on 70 percent bone powder scaffolds showed gene activity hundreds of times higher in three genes indicative of bone formation.
