New 3D printing ink can make synthetic bones for people

Researchers at Northwestern University in the US have created a 3D printable ink that creates a synthetic material implantable in human patients and that quickly induces bone regeneration and growth.

The researchers are calling the ink a type of "hyperelastic bone" (HB) material that can be easily customised, making it especially useful for the treatment of bone defects in children.

"Adults have more options when it comes to implants," Ramille Shah, who led the research, said in a Northwestern School of Engineering news release. "Paediatric patients do not. If you give them a permanent implant, you have to do more surgeries in the future as they grow. They might face years of difficulty."

A cross-section of a 3D printed adult human femur using the new hyperelastic bone ink.

The research was recently published in the American Association for the Advancement of Science's peer-reviewed journal Science Translational Medicine.

The HB biomaterial is made almost entirely from hydroxyapatite, a calcium mineral found in human bone. The hydroxyapatite is mixed with a small amount of a biocompatible and biodegradable polymer (polycaprolactone), which has traditionally been used in medical applications including sutures. Once surgically implanted, the custom bone acts as a highly absorbent and porous scaffolding that triggers a patient's body to begin fusing real bone to it.

The HB material can be printed at a rate of up to 108 inches per hour.

The researchers have so far tested the HB material on a rhesus macaque monkey and was effective at quickly synthesising with existing bone while not eliciting a negative immune response.

The material has also been tested as a rat's spinal fusion model for new bone formation and observed over a two-month period. This also did not elicit a negative immune response, became vascularized, quickly integrated with surrounding tissues, and rapidly ossified and supported new bone growth without the need for added biological factors.

"Porosity is huge when it comes to tissue regeneration, because you want cells and blood vessels to infiltrate the scaffold," Shah said. "Our 3D structure has different levels of porosity that is advantageous for its physical and biological properties."

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