Liposome-Coated Metal Stents: Anin VitroEvaluation of Controlled-Release Modality in the Ureter

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Abstract
Purpose: In vitro preparation of liposome-covered metal stents and loading of liposomal drug formulations that will slowly release the drug in the vicinity of the stent. Materials and Methods: Polytetrafluoroethylene-coated stents were used. Large multilamellar (MLV) liposomes (phosphatidylcholine:cholesterol 1:1 mol/mol), empty or entrapping the corticosteroid anti-inflammatory drug, dexamethasone, were prepared by the thin-film hydration method and applied to pieces of stent using a simple and mild evaporation technique. Initially, a freeze-drying method for applying liposomes to stents was also evaluated, but it failed to produce stents that efficiently retain liposomal lipid when incubated in an aqueous environment. The presence of liposomes on the stent surface was confirmed by scanning electron microscopy. Results: After analyzing the release of liposomal lipid (using a phospholipid assay) and liposomal drug (by a modified dexamethasone high-pressure liquid chromatography method) in an in v...