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Chemists Trying for Plastic Blood Vessels

February 07, 1988|DELTHIA RICKS | United Press International

Chemists are attempting to modify the surface of certain plastics in the hope of developing advanced bionic materials that ultimately can be used as implantable blood vessels.

Experiments under way at the Los Alamos National Laboratory in New Mexico join a growing repertoire of potential uses of plastic to replace malfunctioning physiological systems.

Recent developments include plastic hearts, ventricles, an artificial knee and portions of inner-ear implants that electronically zap sound impulses to the cochlea, the small coiled bone of the inner ear, which then transmits them to the auditory nerve and on to the brain.

The new work with artificial blood vessels could have applications for heart-bypass surgery patients if scientists can figure out how to make plastics adaptable to the complex human circulatory system.

'Obvious' Benefit

"The benefit of having artificial blood vessels immediately available in emergencies is obvious," said Los Alamos chemist Diane Wrobleski, but she also acknowledged that "small, synthetic vessels that do not close or cause the blood to clot" are several years down the road.

Wrobleski and her team face the same formidable challenges that have plagued manufacturers of artificial hearts: when blood comes in contact with any artificial surface it tends to clot, a critical condition that can block circulatory pathways. Guarding against the obstructions is important because clots can lead to heart attacks and strokes.

Recent studies at the University of Pittsburgh showed that a test group of Jarvik-7 artificial heart recipients fared poorly because of infections and severe clotting associated with the mechanical pump. The human body does not reject an artificial material as it would a transplanted human organ but instead develops clots at the point of connection between the body and the artificial material.

The clots then enter the circulatory system.

Wrobleski hopes to sidestep the clotting problem by altering the surfaces of plastics in ways that would reduce chances of blood adversely reacting with the artificial material.

Modifying Surface

Los Alamos scientists are experimenting with a process called chemical infusion to modify the surface of plastics while not changing the material's basic properties of flexibility and strength.

Wrobleski says the chemical process involves placing the plastic in a solution that softens the outside while different chemicals are "infused" into the structure of the surface rendering it adaptable to biological systems.

"The initial results show that the technique of treating the surfaces is promising, but we still need to do a lot of work," she said. "We want to try different infusant materials to test their effectiveness."

The chemist and her team hope to eventually develop a computerized catalogue of specially developed plastic vessels, permitting doctors to shop for those that meet specific medical needs.

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