Multilayer approach for tuning the drug delivery from poly(3-hydroxyalkanaoate)s coatings

A first feasibility study about the sirolimus release from stent coatings based on degradable poly(3-hydroxyalkanoate)s PHAs is reported. Natural poly(3-hydroxybutyrate-co-3-hydroxyvalerate) PHBHV, poly(3-hydroxyoctanoate) PHO, functional polyesters containing carboxylic groups PHO75COOH25, and diblock copolymer poly((3-hydroxybutyrate-co-3-hydroxyvalerate)-b-(lactic acid)) P(HBHV-b-LA) were sprayed onto metallic stents. Stress behavior and coating integrity studied by scanning electron microscopy on unexpanded and expanded stents were found to be superior for the PHBHV and P(HBHV-b-LA). Release of sirolimus from these coatings showed an important burst effect of drug whatever the nature of PHAs due to their very low glass transition temperatures. However, bilayer systems offered many options for controlling sirolimus release over months.