3D printing machine used to print bone substitutes© The University of Sydney
Professor Hala Zreiqat is printing bone substitutes at the University of Sydney’s Biomaterials and Tissue Engineering Research Unit. She has developed a technique for 3D printing ceramic so it acts as a bone-strong scaffold containing ingredients needed for the body to foster bone growth at large defect sites.
Healthy bone undergoes a constant process of renewal and growth. The bone substitute developed by the team led by Zreiqat incorporates smart materials, which contain trace elements and nanoparticles designed to promote bone generation. The non-toxic ceramic is porous, so blood and nutrients can also penetrate it. Over time, the ceramic degrades as it is replaced by new bone.
While the idea for these types of scaffolds has been around for some time, they stalled as researchers around the world attempted to retain the bioactive and porous elements, while also recreating the impressive load-bearing and shock absorption abilities of actual bone. Of similar materials approved for clinical use, most are filling materials not intended for critical‐size defects (generally gaps three centimetres or more in humans).
Zreiqat’s team are currently developing and testing novel ceramics that have the strength of cortical bone (the strong dense outer surface of bones). “They are unique. I haven’t seen any scaffold that is as strong and bioactive,” says Zreiqat.
Bone is the most transplanted substance in medicine, with loss or damage resulting from accidents, disease or developmental issues. More than two million bone graft surgeries are performed worldwide each year, and in Australia alone 71,000 people have bone substitutes or grafts inserted to replace hips and knees annually.
Current treatments require either grafting from a secondary site in a patient, which is problematic when there has been significant bone loss, or inserting metal implants, which frequently need replacing as the body changes over time. If realised, this scaffold could significantly reduce the frequent need for multiple surgeries — minimising time, cost and the risk of complications.
Professor Hala Zreiqat © The University of Sydney
“We’re working towards taking a CT scan of the bone defect and feeding it straight into the printing machine, which hopefully would be sitting next to an operating theatre,” Zreiqat says. The new implant, she adds, could be sterilised and inserted by a surgeon within one to two days. The current process can take several weeks. “This is where the uniqueness of our material and discovery comes in. You can design any shape or size, so it can be applied to a really large or small bone defect,” explains Zreiqat.
Trials to test the scaffolds on large-scale bone injuries in sheep have had excellent initial results. In the latest trial of eight sheep, within three months a quarter of critical defects in long bones had completely healed, while 88 percent were fully healed after a year. Human trials are one or two years away.
To approach the issue of mechanical strength and other problems that have arisen during research, Zreiqat harnesses the University of Sydney’s philosophy of ‘unlearning’, which encourages researchers to continually look for perspectives outside their core knowledge base. She deliberately encourages cross-collaboration between a wide range of disciplines. Her team includes material scientists, cell and molecular biologists, chemical engineers, physicists and clinicians. In the future, she also expects to work with designers and architects.
“Science and discoveries are all built around problems you don’t know the answer to,” explains Zreiqat. “So we draw expertise from each other to develop something new. For example, in our approach to materials, we thought about what would happen if we changed the architecture of that material. Working with the mathematical modelling people, we found that just by changing the architecture, you can significantly affect the quality and the type of bone that forms with the body. It’s big, right?”
Zreiqat’s team are also examining how to use the scaffold with tendons, ligaments and cartilage. She hopes that future applications will include the ability to help implant both synthetic cartilage and bone in the knee.