Heparin-modified polylactide as biodegradable hemocompatible biomaterial

Several medical applications may benefit from biodegradable hemocompatible materials. Therefore a commercial biodegradable polylactide (RESOMER^® R208; Boehringer-Ingelheim, Germany) was modified with heparin. The immobilization of heparin was performed by covalent binding with glutaraldehyde as spacer. Reaction conditions were varied to optimize the coupling of heparin. The efficiency of the immobilization and the biological activity of bonded heparin was estimated with a toluidine blue assay and factor Xa assay, respectively. It was shown that an immobilization at ambient temperature and a reaction time of 2 h yielded maximal heparin binding and biological activity. The hemocompatibility of the modified polylactide was tested after blood/material contact with an enzyme immuno assay (EIA) for GMP 140, a marker of platelet activation. The investigated materials were compared with polypropylene and Pellethane^®. After modification it was found that high heparin binding and biological activity were correlated with very small activation of platelets.