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02-16-2005

Clarkson Polymer Chemist’s Research Looks To Improve Heart Valve Replacement Technology And Patient Outcome

[A photograph for newspaper use is available at http://www.clarkson.edu/news/photos/mueller.jpg]

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

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).”

In her laboratory Mueller is working to perfect a "nonsticky" polymer (or plastic) to coat the outside of the St. Jude's valve material that will inhibit the ability of platelets and other blood ingredients to stick to the device. A "sticky" plastic on the inside of the valve will allow the coating to adhere to the artificial heart valve materials and may even have the potential to have medicines such as anticoagulants incorporated into the valve coating.

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.

Clarkson University, located in Potsdam, New York, is an independent university with a reputation for developing innovative leaders in engineering, business and the arts and sciences. Its academically rigorous, collaborative culture involves 2,700 undergraduates and 400 graduate students in hands-on team projects, multidisciplinary research, and real-world challenges. Many faculty members achieve international recognition for their scholarship and research, and teaching is a priority at every level.  For more information, visit http://www.clarkson.edu.

PHOTO CAPTION: Clarkson University Professor of Chemistry Anja Mueller is working to improve heart valve replacement technology and patient outcome by creating a nonadhesive, medicated polymer coating that will cover the artificial valves and prevent blood platelets and bacteria from building up on the devices. Here, Mueller displays vials containing possible valve coating materials at different stages of development.
[News directors and editors: For more information, contact Michael P. Griffin, director of News & Digital Content Services, at 315-268-6716 or mgriffin@clarkson.edu.]

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