Blood compatibility of tubular polymeric materials studied by biological surface interactions

Tubular polymeric materials modified by radiation techniques can be used as vascular prosthesis and components of prosthetic devices. The biological interaction between these materials and blood was studied by in vitro and ex vivo methods. Silicone rubber tubes were copolymerized with acrylamide and N-vinylpyrrolidone by radiation-grafting techniques. The irradiation was performed with gamma-rays from a 60Co source at a constant dose rate (0.2 kGy/h) for various time intervals (4-15 h). To evaluate the antithrombogenicity of the grafted tubes, the surface adsorption of 125I-albumin and 125I-fibrinogen was studied. All graft copolymers show a preference for albumin, and the degree of preference appears to correlate with antithrombogenic tendency. In the ex vivo experiment with animals, tubes were implanted in the carotid artery of dogs and the blood flow in the graft copolymers was detected with an ultrasonic flow meter. The blood flow rate in the ungrafted implants decreased more rapidly (stopped completely after 15 to 210 min) compared to the flow rate in the grafted ones (decreased slowly from 38 to 35 ml/min and 70 to 60 ml/min). There was a direct relationship between both methods in the study of blood compatibility of the materials. The results suggest that the graft copolymers can be used as biomaterials for long-term use in cardiovascular systems.