Drug release from a chemically-anchored PEG/phospholipid monolayer onto polymer-coated metallic stents.

We have prepared a covalently-grafted phsopholipid/PEG mixed monolayer onto drug-loaded polymercoated stainless-steel stents by in situ polymerization. To introduce a biocompatile surface on the stent surface, AcPC (1-palmitoyl-2-[12-(acryloyloxy)dodecanoyl]-sn-glycero-3-phosphocholine) and AcPEG (12-(acryloyloxy)dodecanoyl-poly(ethylene glycol)) were synthesized by modifying phospholipid and PEG with 12-(acryloyloxy)-1-dodecanoic acid and 12-(acryloyloxy)-1-dodecanol, respectively. Also, an acrylated co-polymer was synthesized by the acrylation of poly(octadecyl acrylate-co-hydroxybutyl acrylate, poly(OA-co-HA)) with acryloyl chloride, and poly(OA-co-HA) loaded with a hydrophobic drug, echinomycin, was coated on the stent surface using a spray coating system. In situ polymerization was carried out at the interface between a pre-assembled AcPC/AcPEG mixture and the enchinomycin-loaded acrylated co-polymer-coated stainless steel (Pol-SS). The physicochemical properties of a covalently-grafted phsopholipid/PEG mixed monolayer onto the drug-loaded polymer-coated stainless-steel stents were evaluated using water contact angle, field-emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS). The data confirmed a successful phsopholipid/PEG monolayer grafting on the stents surface. The drug-release profile showed a sustained and controllable release pattern by the top-coated stents, achieved by adjusting the amount of loaded drug.