Ar-H2O-NH3 plasma grafting and polymerization of dopamine onto polytetrafluoroethylene to promote heparin immobilization

The surface of polytetrafluoroethylene (PTFE) is activated by argon (Ar), Ar mixed with water vapor (Ar-H2O), and a mixture of Ar, water vapor, and ammonia (Ar-H2O-NH3) plasmas and then grafted onto polymerized dopamine/ethylene imine and immobilized heparin. Oxygen-containing functional groups are all introduced onto the PTFE surface treated by three types of plasma. The amount of oxygen grafted is the highest in samples treated with Ar-H2O-NH3 plasma compared to that treated with Ar-H2O plasma. An increase in the content of oxygen grafted onto PTFE contributes to an increase in the thickness and cross-linking bond of the polymeric interlayer and then raises the density of the heparin coating. The thickness of the polydopamine/polyethylenimide intermediate layer on the surface of PTFE treated with Ar-H2O-NH3 plasma is 4.8 +/- 0.3 mu m, and the density of the immobilized heparin coating was 95 mu g/cm(2).