Injectable gels could help repair heart tissue and spinal cord injuries

A team of researchers at McGill University in Montreal and another at Northwestern University in Chicago have developed new techniques that use injections of gel-like materials to facilitate the repair of systems in the body that are difficult to treat.

When it comes to medicine, we often think of treatments to repair the body in the form of invasive surgery or drugs to promote healing. But these two new approaches involve simple injections of special gels that can be delivered directly to the site of injury and help with the repair process.

The first example involves a hydrogel that's tough and flexible enough to create a healing structural environment when injected into dynamic tissues like a beating heart or vocal cords. 

The problem with tissues like heart muscle is that the heart never stops beating, so anything injected into them will have difficulty maintaining its structure without fracturing. That makes it difficult for cells and blood vessels to grow into the injured site. It's one of the reasons plastic bandages were designed to be flexible to stay in place even on a kid that never stops moving. 

Most hydrogels either aren't strong enough to withstand the motion of the heart or vocal cords, or not porous enough for cells to proliferate within them and allow gases or nutrients to pass through. 

VIDEO The vocal cord bioreactor simulates the biomechanics of vocal cords to test the hydrogels.

The new gel hits the sweet spot, so it can not only withstand and flex along with the extreme biomechanical motions of certain tissues, but also create a structure that promotes the growth of new cells and the transport of crucial gases and nutrients. 

To test the gel's durability, the scientists rigged up artificial vocal cords made of the gel material that vibrated 120 times per second for two hours a day, seven days a week — through 6 million cycles of openings and closings, without breaking. 

When they tested how well one of the main cell types in the vocal cords could grow within the gel, they found it provided a cell-friendly three dimensional growing environment. 

The scientists believe the gel could restore the voice of those suffering from laryngeal cancer or be used for heart muscle repair and drug delivery, all by simple injection.

The second group developed materials that can self-assemble into nanofibres with biological signals that can trigger cells to repair and regenerate in damaged tissues, like with a spinal cord injury, which otherwise would not heal. 

Starting out as a liquid, the biologically active materials form nanofibres that turn into a gel, which mimics the environment of the spinal cord. By tweaking the structural part of the nanofibre-forming materials, the researchers got them to vibrate in just the right way to connect with nerve cells.  

The more dynamic the motion was or the more the molecules danced, the better the nerve cells were able to grow and reconnect. The treatment also encouraged the growth of myelin, a sheath that forms around the nerves to protect them from further injury, like the plastic coating around an electrical wire.

This therapy has the potential to change the lives of those with complete spinal injury where less than 3 per cent of people fully recover basic functions. While this treatment is only a lab experiment performed on mice at the moment, the researchers are looking for federal approval to move forward on clinical trials on humans.