Effect of surface texture of grafted films on antithrombogenicity

The relation between grafting conditions and antithrombogenicity has been examined from the purpose of clearing the necessity of controling grafting conditions to enhance blood compatibility. The grafting systems employed here were N, N-dimethylacrylamide (DMAA) — poly(tetrafluoroethylene) (PTFE) and DMAA- poly(ethylene-co-tetrafluoroethylene) (AFLON) and grafting parameters were dose rate, monomer concentration and total dose (irradiation time). Grafting DMAA onto the substrates was carried out by using simultaneous irradiation method of gamma rays from a ⁶⁰Co source. After evaluation of blood compatibility of the grafted films by using in vitro tests, it has been clear that control of grafting conditions is important. Especially, in both grafting systems, dose rate control has found to be very important for blood compatibility. When higher dose rate of 1.0 × 10⁵ to 3.0 × 10⁵ rad/hr was used for grafting DMAA onto PTFE or AFLON, blood compatibility of the substrates was not enhanced, whereas it was improved when the grafting was carried out at lower dose rate of 0.97 × 10⁴ rad/hr. The correlation between dose rate and antithrombogenicity has been interpretated in terms of surface-roughness of the grafted films. By scanning electron microscope (SEM) — observation, it has been observed that higher dose rate makes the surface rough, whereas lower dose rate does it smooth. In the grafting systems used here, therefore, dose rate is the most important factor to control the roughness of surface which gives a profound effect on antithrombogenicity.