An x-ray of a hand with a severely broken thumb.
An x-ray of a hand with a severely broken thumb.

A biodegradable implant encourages the natural repair of broken bones using heat

We all know that heat can soothe injuries, but it can also directly encourage repair of broken bones. An innovative biodegradable bone implant can release localised heat, which in turn stimulates the natural regeneration of damaged bone. As the bone heals itself the implant degrades, offering a powerful new tool to repair large-scale bone damage.

The development and early testing of the procedure, using live rats and cultured cells, is reported in the journal . The research team behind the procedure is based in China and led by Huaiyu Wang at the Shenzen Institutes of Advanced Technology, Chinese Academy of Sciences.

“Our research is demonstrating that biomaterials can be designed with smart biofunctions that can be controlled by external stimulation,” says Wang. He decided to combine the benefits of heat for bone healing with modern materials that can be stimulated by external factors, such as light.

The bone implants the team has developed incorporate extremely thin nanosheets of  into the polymer . This composite material is stimulated to release heat when it absorbs . This is the form of light that penetrates most deeply into body tissues. It can shine through what has become known as the body's 'therapeutic window', which is transparent to light and can assist healing or stimulate the release of drugs.

The material was initially tested on rats. Initial tests revealed that 10 weeks after implantation, treated animals experienced around twice as much bone regeneration, compared to untreated controls.

The researchers hope that their implants could be manufactured by  technology. This will enable them to precisely match the regions of damaged bone that need to be repaired.

Examining the effect of the implanted material on cultured cells also offered significant insights into the molecular mechanisms involved in bone regeneration. These involve increased production of , a category of repair proteins that are produced in cells exposed to stresses, such as raised temperatures.

As the implant slowly biodegrades, it is converted into harmless water, carbon dioxide and phosphate ions. These can be used as raw material for making new bone.

“Our strategy is operationally simple and readily fine-tuned,” says Wang. He does acknowledge, however, that some challenges remain on the road from the current proof-of-principle work to application in the clinic. Fractures in patients are often covered by thicker tissues than in laboratory animals, for example, but Wang hopes this might be overcome with more highly powered near-infra-red light and by increasing the black phosphorus in the implants.

Article details:

Wang, H., et al.: “Near-infrared light control of bone regeneration with biodegradable photothermal osteoimplant” Biomaterials (2019