Liposome-coated metal stents: an in vitro evaluation of controlled-release modality in the ureter.
OBJECTIVE
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.


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 vitro system developed to simulate in vivo conditions, it was found that 39.11+/-6.8% of the lipid and 50.84+/-5.48% of the drug was released from the stent pieces during 48 hours of incubation in the presence of artificial urine. The amount of dexamethasone released from stents during their application procedure was found to be negligible in an in vitro dry run.


CONCLUSIONS
The use of stent-associated liposomal drug formulations as slow-release depots could be an efficient method of treating the untoward event of ureteral stent obstruction.
Antimisiaris
S G
SG
Department of Urology, University of Patras, School of Medicine, Greece.
Siablis
D
D
Liatsikos
E
E
Kalogeropoulou
C
C
Tsota
I
I
Tsotas
V
V
Karnabatidis
D
D
Fatouros
D G
DG
Barbalias
G A
GA
D002851:Chromatography, High Pressure Liquid; D020099:Coated Materials, Biocompatible; D003907:Dexamethasone / Q000008:administration & dosage* / Q000032:analysis; D004343:Drug Implants; D005938:Glucocorticoids / Q000008:administration & dosage* / Q000032:analysis; D006801:Humans; D066298:In Vitro Techniques; D008081:Liposomes / Q000737:chemistry; D008670:Metals; D011138:Polytetrafluoroethylene; D019919:Prosthesis Implantation / Q000295:instrumentation*; D014513:Ureter / Q000601:surgery*; D014517:Ureteral Obstruction / Q000188:drug therapy / Q000209:etiology / Q000601:surgery
D020099:Coated Materials, Biocompatible; D004343:Drug Implants; D005938:Glucocorticoids; D008081:Liposomes; D008670:Metals; D003907:Dexamethasone; D011138:Polytetrafluoroethylene