Buddy Ratner said the body's instinct to ``wall off'' a foreign object means that science, in the quest to improve medical implants, needs to create smarter polymers.
``Biomaterials should look to the body like biomolecules. But, certainly, at the moment, most of the biomaterials look more like auto parts to the body,'' Ratner said May 5 at Antec 2003, held in Nashville.
Ratner is director of the University of Washington's Engineered Biomaterials center, funded by the National Science Foundation. He specializes in the interaction of biomaterials - such as plastics-intensive implants - and their interactions with the biological systems.
Some 70 percent of all biomaterials are polymeric, Ratner said, as he ran through well-known implants such as interocular contact lenses, pacemakers, membranes for kidney dialysis and the artificial heart.
``So it's a pretty rosy picture for the use of polymers in medicine,'' he said. ``But how well do they work?''
With interocular lenses, a second operation is needed in 25-50 percent of cases. Hip and knee replacements last just 10 or 15 years. Problems with catheters lead to many deaths a year, Ratner said.
One major problem is the body's natural protection, which encapsulates foreign objects inside a sac covered with a layer of proteins. Implants designed to deliver regular doses of drugs end up releasing them into the closed-off bag. Electrical signals to control medical devices inside the body also can be blocked.
``The implant is really just walled off and the body's gotten rid of it. In fact, the reaction's not all that different from when you get a splinter,'' Ratner said.
The Engineered Biomaterials center is a consortium of 20 professors, 100 students and 26 biomedical-device companies. A major goal is improving how the body heals after biomaterial implants. Ratner said the researchers want future implanted materials to be truly biocompatible, so the body heals like it does with a normal wound.
Ratner, a polymer chemist who was elected to the National Academy of Engineering last year, told Antec attendees about some futuristic ideas. Microscopic machines could repair blood cells, or release insulin or cancer-fighting drugs as needed. Implants that detect brain impulses could make a paraplegic walk. Stainless-steel stents could be coated with a ``smart gel'' that picks up inflammation of a blood vessel and automatically releases medicine to get it under control.
``I think we're entering a kind of remarkable era,'' Ratner said.