New 3-D printable ink for rapid bone regeneration

Researchers have developed a 3-D printable ink which can produce a synthetic bone implant that rapidly induces bone regeneration and growth.
The hyperelastic "bone" material, whose shape can be easily customised, may be especially useful for the treatment of bone defects in children, researchers said.
Bone implantation surgery is never an easy process, but it is particularly painful and complicated for children. With both adults and children, often times bone is harvested from elsewhere in the body to replace the missing bone, which can lead to other complications and pain.
"Adults have more options when it comes to implants," said Ramille N Shah from Northwestern University in the US.

"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," said Shah, who led the research.
Shah's 3-D printed biomaterial is a mix of hydroxyapatite - a calcium mineral found naturally in human bone - and a biocompatible, biodegradable polymer that is used in many medical applications, including sutures.

The hyperelastic "bone" material shows great promise in in-vivo animal models; this success lies in the printed structure's unique properties.
It is majority hydroxyapatite yet hyperelastic, robust and porous at the nano, micro and macro levels.

"Our 3-D structure has different levels of porosity that is advantageous for its physical and biological properties," he said.
While hydroxyapatite has been proven to induce bone regeneration, it is also notoriously tricky to work with. Clinical products that use hydroxyapatite or other calcium phosphate ceramics are hard and brittle.
Shah's bone biomaterial is 90 per cent by weight per cent hydroxyapatite and just 10 per cent by weight per cent polymer and still maintains its elasticity because of the way its structure is designed and printed.
The high concentration of hydroxyapatite creates an environment that induces rapid bone regeneration.

"Cells can sense the hydroxyapatite and respond to its bioactivity," Shah said.
"When you put stem cells on our scaffolds, they turn into bone cells and start to up-regulate their expression of bone specific genes. This is in the absence of any other osteo-inducing substances. It's just the interaction between the cells and the material itself," she said.
Since the 3-D printing process is performed at room temperature, Shah's team was able to incorporate other elements, such as antibiotics, into the ink.
"We can incorporate antibiotics to reduce the possibility of infection after surgery," Shah added.
The study was published in the journal Science Translational Medicine.