Vascular stenting has been one of the most successful aspects of modern medicine, helping to treat a number of common conditions that were otherwise deadly or required bypass procedures. After placement, stents provide a rigid structure around which the vessels heal, but they remain implanted even after they’re no longer needed. So far Abbott has been leading the effort to offer a way to “remove” a stent by developing its ABSORB vascular scaffold. The bioresorbable stent is made of polylactide, a material commonly used to make dissolving sutures. Iron and magnesium have been metals tried by other teams, but they rust and dissolve too fast.
Now researchers at Michigan Tech have shown that zinc may be a better option. The team placed very narrow zinc wires inside the arteries of rats and monitored how they were adopted by the body and degraded over time.
“The corrosion rate was exactly where it needed to be,” [Patrick Bowen, a doctoral student studying materials science and engineering at Michigan Technological University] said. The wires degraded at a rate just below 0.2 millimeters per year—the “magic” value for bioabsorbable stents—for the first three months. After that, the corrosion accelerated, so the implant would not remain in the artery for too long. On top of that, the rats’ arteries appeared healthy when the wires were removed, with tissue firmly grasping the implant.
“Plus, zinc reduces atherosclerosis,” he added, referring to zinc’s well-known ability to fight the development of plaque in the arteries. “How cool is that? A zinc stent might actually have health benefits.”
There is one drawback. “A stent made of conventional zinc would not be strong enough to hold open a human artery,” he said. “We need to beef it up, double the strength.”
“The good news is that there are commercial zinc alloys that are up to three times stronger,” Bowen said. “We know we can get there. We just don’t want to ruin our corrosion behavior.”
The researchers have filed a provisional patent on their discoveries and are now testing new zinc-based stent materials.
Study in Advanced Materials: Zinc Exhibits Ideal Physiological Corrosion Behavior for Bioabsorbable Stents
Michigan Tech press release: Zinc: The Perfect Material for Bioabsorbable Stents?