Comparative Evaluation of Physicochemical and Biological Characteristics of Polylactides and Lactide–Glycolide Copolymers for Biodegradable Vascular Stent Coatings

A biodegradable polymer coating on a permanent metallic vascular stent must combine mechanical stability during deployment, hemocompatibility, and controlled resorption without a pronounced local inflammatory response. The aim of this study was to compare the physicochemical characteristics and physiologically relevant biological responses of six commercial polymers based on polylactide and its copolymers with glycolide, differing in stereoregularity (L- and DL-lactide), monomer ratio (50/50, 75/25, 90/10), and end-group type (ester or acid), in order to select a material for further development of a biodegradable stent coating. Equilibrium swelling and tensile properties were examined using model free-standing films; for five materials that could be prepared as intact films, hemolysis, platelet activation in vitro, biodegradation, and local tissue response after 30-day subcutaneous implantation in Wistar rats were assessed. Crystalline poly(L-lactide) and the copolymer containing 10% glycolide exhibited high stiffness and low elongation at break; the latter was excluded from biological testing because of film brittleness. Copolymers containing 50% glycolide were highly ductile. None of the biologically tested materials caused pronounced hemolysis or platelet activation. On day 30, the faster-degrading PLGA(50/50)-E, PDLLG(50/50)-A, and PLGA(75/25)-E showed pronounced resorption with minimal local inflammation, whereas slowly degrading PDLLA-E and PLLA-A persisted in the tissues and were associated with a more pronounced chronic foreign body response. PLGA(75/25)-E showed the most balanced combination of mechanical properties, degradation behavior, and biological response profile. These data support its selection as a candidate for the next stage, namely deposition on a metallic stent platform and evaluation as an actual stent coating.