As populations age, the incidence of conditions such as osteoarthritis and osteoporosis inevitably increase, in turn precipitating a growing demand for orthopedic implants. Although titanium (Ti) has been widely used in bone replacements, the metal does not always integrate readily with the surrounding bone, resulting in implant failure.
Porous Ti materials containing magnesium (Mg)—an essential element for bone formation—may encourage bone growth by releasing Mg ions and allowing bone cells to enter the pores of the implant. However, it is difficult to synthesize a strong network of interconnected pores using conventional fabrication methods.
In the present study, researchers led by Sharon Nai, a Senior Scientist at A*STAR's Singapore Institute of Manufacturing and Technology (SIMTech), fabricated Ti + Mg composite implant parts using 3D printing and characterized their strength, resistance to corrosion as well as toxicity to cells. The biocompatibility studies were done in collaboration with researchers at the National University of Singapore.
“3D printing enables fast, accurate and cost-effective fabrication of porous biomedical implants with improved fit and load distribution specific to patients’ requirements,” said Ganesh Kumar Meenashisundaram, a Scientist at SIMTech and the lead author of the study.
The team 3D-printed porous Ti parts in two different shapes: the first was a cylinder, and the other was a cylinder with a cup structure attached to one end. “Post 3D printing, the Ti parts were cured at 150 oC for two hours and thermally debinded and sintered at 1200 oC under argon gas atmosphere,” Meenashisundaram explained.
Microscopy revealed that the porous Ti material contained well-interconnected pores. The team then successfully infiltrated these pores with molten Mg to create Ti + Mg composites.
The researchers showed that their 3D-printed porous Ti and 3D-printed Ti + Mg composites were similar in strength to human bone and could withstand high strain without fracturing. When immersed in a saline solution of 0.9 % sodium chloride to simulate exposure to chloride ions in the body, the researchers observed negligible corrosion of both materials. Neither material was toxic to bone cells, and in the case of Ti + Mg composites, the leaching of Mg ions from the composites stimulated bone cell infiltration and proliferation.
“Moving forward, we will perform in vivo tests to confirm the suitability of Ti + Mg composites as a potential implant material. We also plan to optimize the 3D printing parameters and investigate the use of biomedical-grade titanium alloys,” said Meenashisundaram, adding that the findings from this study may pave the way for the design of orthopedic implants with improved implant success rates.
The A*STAR-affiliated researchers contributing to this research are from the Singapore Institute of Manufacturing and Technology (SIMTech).