Under the needle, not under the knife

University of Toronto researchers develop cardiac repair patch that can be injected

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TORONTO—In everyday life, the idea of patching something is often seen as a quick-fix or a half-solution. On the other hand, when it comes to something that is very difficult to replace, like the human heart, patching may be the future of treating many cardiac injuries or defects.
As noted in the March 2016 article “Application of Biomaterials in Cardiac Repair and Regeneration” in the journal Engineering, “Although pharmacological and surgical interventions dramatically improve the quality of life of cardiovascular disease patients, cheaper and less invasive approaches are always preferable. Biomaterials, both natural and synthetic, exhibit great potential in cardiac repair and regeneration, either as a carrier for drug delivery or as an extracellular matrix substitute scaffold.”
Further, from the market insight angle, there is the “Cardiovascular and Soft Tissue Repair Patches Market Analysis by Application and Segment Forecasts to 2022” report from Grand View Research that notes the global cardiovascular and soft tissue repair patches market size was valued at $2.49 billion in 2014 and is expected to reach nearly $5.79 billion in 2022.
At the University of Toronto, biomedical engineering professor Milica Radisic and her colleagues may have found a way to avoid opening up a patient’s chest to put such patches in place, having recently developed a technique that lets them use a small needle to inject the repair patch.
It was an almost three-year journey with dozens of attempts by Miles Montgomery, a Ph.D. candidate in Radisic’s lab, to achieve this, and he said: “At the beginning, it was a real challenge. There was no template to base my design on, and nothing I tried was working. But I took these failures as an indication that I was working on a problem worth solving.”
But Montgomery did achieve a design that, as the University of Toronto notes, “matched the mechanical properties of the target tissue and had the required shape-memory behavior: as it emerges from the needle, the patch unfolds itself into a bandage-like shape.”
“The shape-memory effect is based on physical properties, not chemical ones,” added Radisic, which means that the unfolding process would not require additional injections nor be affected by the local conditions within the body.
Once the mechanical hurdle was overcome, the research team seeded the patch with actual cardiac cells, let them grow for a few days and then injected them into rats and pigs, finding that not only did the injected patch unfold to almost the same size as a patch implanted by more invasive methods, the heart cells survived the procedure well. The team also showed that injecting the patch into rat hearts can improve cardiac function after a heart attack—the damaged ventricles pumped more blood than they did without the patch.
“When we saw that the lab-grown cardiac tissue was functional and not affected by the injection process, that was very exciting,” says Montgomery. “Heart cells are extremely sensitive, so if we can do it with them, we can likely do it with other tissues as well.”
And, in fact, as they apply for patents on the invention, they are also exploring the use of the patch in other organs, such as the liver, with Radisic noting, “You could customize this platform, adding growth factors or other drugs that would encourage tissue regeneration.”
The scaffold is built out of a biocompatible, biodegradable polymer so that, over time, the scaffold will naturally break down and simply leave behind the new tissue.
Clinical trials in humans remains a fairly distant goal; currently, Radisic and her team are collaborating with researchers at the Hospital for Sick Children to assess the long-term stability of the patches, as well as whether the improved cardiac function can be maintained.

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