Development of New Coronary Stent-Grafts using Surface-Modified Polymers

ABSTRACT

BACKGROUND AND OBJECTIVE: The purpose of this study was to develop a new type of coronary stent-graft, using surface modification of polymeric synthetic graft materials, to improve biocompatibility. MATERIALS AND METHODS: Three different polymers, Dacron, GoreTex and Teflon were tested. During the surface-modification process, hydroxybutyl acrylate (HBA) choline, an excellent blood-compatible phospholipid, was stably grafted onto the polymer surface. The optimal conditions for maximizing the amount of HBA choline grafted onto the polymeric surface were determined by quantitative analysis. The surface-modified polymers were then tested for their biocompatibility using an in vitro platelet adhesion test. Thereafter, stent-grafts were constructed with each of three different types of surface-modified polymer and implanted in porcine coronary arteries to compare their biocompatibility in vivo. RESULTS: In the platelet adhesion test, all the surface-modified polymers showed better biocompatibility than the control polymers. The in vitro biocompatibility correlated positively with the increasing quantity of grafted HBA choline. In the animal experiment, the surface-modified Teflon stent-graft showed the best biocompatibility. Whereas, all pigs implanted with the modified Dacron and GoreTex stent-grafts died within 48 hours of the implantation, five out of the six pigs with the Teflon stent-grafts remained alive at after the 4th week. In four of the five surviving pigs, angiography, intravascular ultrasound (IVUS) and histological evaluations demonstrated the patency of the stent-grafts, with a uniform neointima formation covering the entire stent-graft, without stent thrombosis or chronic inflammatory cells. CONCLUSION: The surface-modified Teflon coronary stent-grafts showed good in vitro and in vivo biocompatibility. Further animal and clinical studies will be required to validate the efficacy of the surface-modified polymer stent-grafts.