In vitro and in vivo characterisation of biodegradable polymer-based drug-eluting stent

The objective of this study was to investigate the structural integrity and early vascular response of a polylactic acid-coated (i.e., biodegradable polymer) coronary drug-eluting stent (DES) (BioMatrix™; Biosensors International, Singapore) to three currently marketed FDA/CE- mark approved non-erodible polymer-coated DES in a porcine model.

BioMatrix™, XIENCE V™ (Abbott Vascular, Santa Clara, CA, USA), TAXUS® Liberté™ (Boston Scientific, Natick, MA, USA), and Cypher SELECT™ (Cordis, Johnson & Johnson, Miami, FL, USA) stents were implanted in pig coronaries for seven days. Polymer integrity was assessed by scanning electron microscopy (SEM) following tissue digestion. In vitro expansion of the BioMatrix™ was also performed. SEM analysis of in vivo stents demonstrated polymer defects on the abluminal surface of all DES including polymer cracking (BioMatrix™), bridging (TAXUS Liberté™), round-small defects (Cypher SELECT™), and flaking (XIENCE V™). Histologically, the myocardium revealed no evidence of acute myocardial infarction or microscopic scarring, moreover all intramyocardial vessels were found to be patent with no evidence of emboli. In vitro results demonstrated greater BioMatrix™ polymer cracking and lifting.

These results illustrate the presence of polymer defects in all DES (TAXUS Liberté™, Cypher SELECT™, XIENCE V™, BioMatrix™) implanted seven-days in pigs, with absence of myocardial damage in this small number of samples. Polymer coating irregularity was greater in BioMatrix™ stent expanded in vitro as compared to in vivo, suggesting simulated benchtop deployment induces greater damage to the biodegradable polymer coating than in vivo deployment in healthy porcine coronary arteries.