STUDIES ON A NEW RADIOPAQUE POLYMERIC BIOMATERIAL

A new radiopaque polymeric biomaterial has been synthesized. The material, which actually represents an entire family of analogous radiopaque materials, is composed of 2-(p-iodobenzoyl)ethyl methacrylate (compound 1, 21 mol%), methyl methacrylate (MMA, 60 mol%), and 2-hydroxyethyl methacrylate (HEMA, 19 mol%). The terpolymer was synthesized in a radical polymerization reaction at elevated temperature in N,N-dimethylformamide (DMF). The product was subjected to a set of physicochemical characterization techniques (gel permeation chromatography, 500 MHz H-1 NMR in deuterated dimethylsulphoxide (d(6)-DMSO) solution, differential scanning calorimetry, dynamic water contact angle measurements), as well as to an in vitro thrombogenicity assay. Furthermore, scanning electron microscopy was used to study interactions of the material with blood platelets. The most important findings are: (a) the material is a genuine polymer with excellent X-ray visibility, even in the form of thin (0.4 mm) drawn fibres. This was established under realistic conditions. (b) The material exhibits low in vitro thrombogenicity, i.e. comparable to polyvinyl chloride, which is known as a passive material. These observations lead us to the suggestion that this type of radiopaque polymer holds promise with respect to application as a construction material for a new type of endovascular stent. This could be relevant in particular to stents to be used in conjunction with percutaneous transluminal coronary angioplasty (PTCA), also known as Dottering. Currently there is a clear trend away from metallic stents towards all-polymeric stents, since the latter have superior biocompatibility. Biocompatibility of the stent material is of vital importance with respect to the long-term performance of the stent, i.e. its ability to prevent the phenomenon of restenosis. Note that both stent material-vessel wall and stent material-blood interactions are crucial. Application of a radiopaque polymer as described herein should enable us to construct a new stent type with improved biocompatibility with respect to the metallic counterparts, combined with excellent X-ray visibility.