Engineering news
Designed as a lightweight material for potential bone repair applications, the composite and manufacturing methods were developed at EPFL university in Lausanne, Switzerland.
Inspired by the resilient and self-repairing mechanical properties of bone, researchers have been developing synthetic materials using a mineral called hydroxyapatite (HA). Processes to produce HA-based materials typically involve high temperatures, however, requiring significant energy and restricting the use of biologically active components, such as enzymes, to promote bone growth.
Researchers at EPFL’s School of Engineering have now developed a way to 3D-print HA-based scaffolds using a room-temperature process that harnesses enzymes for fast mineralisation.
“Our idea was to generate a 3D-printable and injectable ‘ink’ that can be mineralised into scaffolds with mechanical properties similar to those of highly porous trabecular bone, which is found in human vertebrae and the ends of long bones like the femur,” said Soft Materials Laboratory head Esther Amstad.
The team’s ink is produced by embedding the enzyme alkaline phosphatase into gelatin microparticles, then incubating them in a solution with calcium and phosphate ions. The enzyme triggers the formation of HA crystals that stiffen and strengthen the printed scaffolds.
The scientists also added enzyme-free gelatin microfragments, which melt when the scaffold is incubated, leaving pores behind. After implantation at the site of a bone fracture, those pores could be replaced by healthy cells to promote the growth of new bone. Tuning the density of those microfragments would allow the team to control the scaffold’s porosity.
By introducing pores that make up about 50% of the scaffold volume, the researchers create room for cells to infiltrate and ‘remodel’ the scaffolds, opening new possibilities for natural bone regeneration.
“We hope that our technology’s combination of mechanical performance, bioactivity and energy-efficient processing will open new avenues for bone tissue engineering,” Amstad said.
In one experiment, 14 days after seeding scaffolds with human stem cells and placing them in a bone growth-supporting medium, the researchers detected the presence of collagen and the bone matrix protein osteocalcin – both indicators of cell growth.
The team’s enzyme-aided approach yields HA scaffolds that are stronger than those produced via high-temperature methods, Amstad said, demonstrating compressive strength comparable to that of human trabecular bone. The technique could be used to print highly complex scaffolds and can be done using commercially available bioprinters.
“Looking ahead, our work might lay the foundation for injectable scaffolds that aid bone regeneration and potentially enable patients to load their broken bones much earlier than can be achieved with currently available technologies,” she said.
The research was published in Advanced Functional Materials.
Want the best engineering stories delivered straight to your inbox? The Professional Engineering newsletter gives you vital updates on the most cutting-edge engineering and exciting new job opportunities. To sign up, click here.
Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.