News
| 16 Feb 2005 | [Printable Version] |
Some 225,000 heart valve replacement procedures are performed each year according to statistics from St. Jude Medical, a leader in the medical technology industry.
But while patient outcome and surgical procedures have improved with time, existing heart valve replacement technology has not been able to find a way to avoid the problems of blood clotting or protein buildup over the device’s lifetime. “This means the valve often needs replacing, causing additional invasive surgeries and medical cost,” explained Clarkson University Professor of Chemistry Anja Mueller. “Also a surgery to replace a valve can only be done two or three times before scar tissue builds up to the point where the heart can no longer function.”
Mueller, a polymer chemist, is working to improve heart valve replacement technology by creating a nonadhesive, medicated coating that will cover the artificial valves and prevent blood platelets and bacteria from sticking to heart valves installed in patients.
“There are currently two types of replacement technologies available to recipients: biological or tissue valves that are taken from an animal or human donor, or mechanical valves that appear to be more durable and have a longer lifespan,” she explained. “Mechanical valves or rings can be made of many different materials, including titanium, silicone rubber, polyester, polypropylene, stainless steel, with the most common heart valve made out of pyrolytic carbon and polyethlene terephthalate (known as St. Jude's valve).”
Mueller is conducting various chemical experiments in the process of polymerization. She is currently working with HRP, or “horse radish peroxidase,” a peroxidase enzyme isolated from the horseradish plant, as the catalyst for the polymerization reaction. HRP has proven to be according to Mueller “a beautiful polymer" that simplifies the reaction and thus helps synthesize a material that at least in its early stages looks promising as a heart valve replacement coating.
“HRP is a fairly stable catalyst for synthesizing polymers allowing for a reproducible and predictable polymer structure. The HRP enzyme also functions in water, obviating the need to introduce harsh or toxic chemicals that could further damage the heart valve,” said Mueller.
In Mueller’s laboratory researchers found that HRP can make aromatic (carbon fiber reinforced) polymers that are similar in structure to pyrolytic carbon, today the most common and durable material used for artificial heart valves and a plastic used more than 30 years ago to coat nuclear fuel particles for gas-cooled nuclear power reactors. The scientists also discovered that HRP can be used to create flexible hydrophilic polymers, which are needed for the nonsticky outside polymer coating.
In the end Mueller’s complex research program, given time and further experimentation, could yield promising results for heart valve technology and may have other biomedical applications as well.
[News directors and editors: For more information, contact Rick Burt, director of Media Relations, at 315-268-3873 or rburt@clarkson.edu .]