Loosening bacteria's hold on implants.

Loosening bacteria's hold on implants

Polymers make it possible for physicians to replace a blocked artery, give a patient a new hip joint or deliver long-term intravenous therapies through catheters. However, the use of these synthetic implants is undermined by Staphylococcus bacteria, which are able to infect nearly all polymers, often necessitating their removal from the body. "Infection of medical devices and implants has become a major problem in prosthetic medicine,' says Bernd Jansen of the University of Cologne in West Germany.

Because adhesion of bacteria to polymers is thought to be the first step in infection, Jansen and his colleagues are exploring ways to discourage bacteria from settling on polymers --a process that is governed by electrostatic and other forces and also by poorly understood interactions between bacterial proteins and other proteins on the polymer. They have preliminary evidence that bacterial adhesion can be reduced if the blood protein albumin coats a polymer. And they have found that they can attract albumin rather than other proteins by modifying the polymer's surface properties. They also have some indication that surface modifications by themselves reduce bacterial adhesion.

Jansen's group is also developing ways to coat polymers with antibiotics and to incorporate antibiotics into the implants. Jansen says that by changing the polymer surface, they can extend the time an antibiotic coat clings to a polymer surface from 10 minutes to one day. Implants embedded with antibiotics continue to release them for more than five days.

Jansen says there is a close relationship between infection and blood clotting, the other major problem of synthetic vascular grafts, since bacteria can stick to clots and clot cells stick to infected surfaces. He says some of the surface techniques he is now using to combat infection were originally developed by him to prevent blood clotting.