“Every time a patient undergoes a dialysis treatment, it’s about $8 worth of anticoagulant that’s used. In North America alone, somewhere on the order of a million dialysis procedures are done a day. Even if you reduced the amount of heparin (anticoagulant) by about one dollar’s worth, that would be one dollar times a million, times 365 days a year. You can see the impact that that has on the cost of healthcare.”
Blood clots inside the body are bad news for patients, which is why clot prevention is a big focus for Paul Santerre, professor of biomedical engineering at the University of Toronto. When clots do form, they can break off and block important arteries, potentially triggering life-threatening complications, including stroke and pulmonary embolism.
Santerre uses chemistry to alter the surfaces of medical devices, making them look invisible to blood cells that might otherwise clot on foreign surfaces.
“Catheters are little plastic tubes that we run through lots of different pathways in the body, but quite often through blood,” says Santerre.
“One of the very first technologies that we developed was a technology that actually changes the chemistry on the surface of the material, and by presenting that diverse chemistry we can actually fool proteins, as they’re interacting with this plastic, to think that they’re still swimming around in blood. And if you can do that with proteins that are involved in the clotting pathway, you can stop clots from happening on these foreign surfaces.”
Santerre’s catheters are so successful that patients with long-term catheter lines, like those undergoing chemotherapy, can go for upwards of two years without developing a clot. And this is also good news because these immunocompromised patients are also at reduced risk of infection when clotting is prevented; clots are made of proteins, which bacteria love to live on. Incidence of infection goes down 800 percent with the modified catheters.
Santerre also uses the same approach to modify the surfaces of fibres in dialysis cartridges. These cartridges function like an artificial kidney to clean the blood, and they contain around 6,000 fibres, which used to be coated individually in a very labour-intensive process.
“What we get to do is extrude these fibres, and as we extrude these fibres, the additive migrates to the surface,” explains Santerre. “Those additives, again, reduce clotting.”
This cuts the cost of manufacturing, and given that patients can be on dialysis for life, those savings can add up.
“It’s a great story of chemistry of materials, production of materials, knowledge of biology, all the knowledge of all those proteins, and how those proteins interact with blood elements that induce clotting,” says Santerre.
“It’s about three decades’ worth of research. This is why we fund fundamental research in Canada: so that we can take that fundamental knowledge and package it all together in the end to create an impactful technology like this.”