Mechanism of failure of biocompatible-treated surfaces

In recent years, significant advances have been made in treating surfaces to enhance their biocompatibility. This has generally involved the chemical attachmet of very thin molecular coatings to a substrate. Because failure of coated surfaces occurs often, an investigation of the stability of one such molecular coating was undertaken. The specific system studied is a polytetrafluoroethylene polymer (Teflon) with organic macromolecules of heparin ionically bonded to the polymer through use of an intermediate bonding agent. Polymers properly treated in this fashion have been shown to have excellent antithrombogenic properties. To investigate the molecular stability of the heparin coating, the surface heparin concentration of a properly coated sample was reduced by using three different methods: exposure of bonding agent to a suitable solvent; mechanical flexing; and ultrasonic vibration in saline solution...