A molecule found in seaweed can promote vascular cell growth and prevent blood clots in the lab, providing early promise of better outcomes in patients undergoing heart bypass surgeries.
University of Waterloo chemical engineer Evelyn Yim and her team say their findings could be especially important in cases involving small artificial blood vessels which are prone to clots that can develop into full blockages.
The team used fucoidan – a long chain sulfated polysaccharide found in various species of brown algae – to modify small artificial blood vessels in a rabbit carotid artery. Fucoidan has a chemical structure much like heparin, a drug used as an anticoagulant. But unlike heparin, fucoidan also promotes the growth of vascular cells on the inner surface of synthetic blood vessels.
It can be hard to get vascular cells to grow on artificial graft material, but without an inner coating of cells, it’s more likely clots will form and develop into full blockages or cause inflammation that restricts blood flow.
Yim likens her team’s approach to laying sod on bare dirt backyard. “A healthy layer of sod prevents weeds from growing,” she says. In the same way, a healthy layer of vascular cells prevents blood clots from forming.
The researchers used a nanotechnology technique known as micropatterning to apply fucoidan to the artificial vessel. Micropatterning creates specifically patterned and textured surfaces. The technique encourages vascular cells to distribute themselves evenly throughout the artificial vessels instead of bunching up at the entrance.
The researchers say they were able to cover 60 per cent of the inner surface of synthetic blood vessel in the rabbit’s carotid artery, compared to 0% for an untreated vessel. It took 28 days to reach this coverage, after which the experiment was concluded.
Yim suspects that when the procedure reaches clinical trials several years from now, human patients will eventually see 100 per cent coverage of the inner surface of their artificial blood vessels.
While using vessels harvested from patients will always provide the best outcome during by-pass surgery, the procedure takes time and can’t be used during emergencies, such as heart attacks.
The team also experimented with a polyvinyl alcohol graft, instead of the Teflon-like material currently used to make artificial vessels. Some researchers believe because the Teflon-like material has a more rigid structure than natural blood vessels, the mechanical mismatch between the two materials can sometimes lead to clots.
While studies have yet to prove this, Yim wanted to experiment with a more pliable graft material. “We can apply this technique to other polymers, but we used polyvinyl alcohol because its mechanical properties are more similar to real blood vessels than the materials we use now,” she says.
The researchers – who describe their approach in the journal Bioactive Materials – say they their findings could have wider applications. Artificial grafts are used in other medical procedures to treat vascular diseases and restore blood flow to vital organs and tissues, including the brain and legs.