Development of Hydrophobized Alginate Hydrogels for the Vessel-Simulating Flow-Through Cell and Their Usage for Biorelevant Drug-Eluting Stent Testing
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The vessel-simulating flow-through cell (vFTC) has been used to examine release and distribution from drug-eluting stents in an in vitro model adapted to the stent placement in vivo. The aim of this study was to examine the effect of the admixture of different hydrophobic additives to the vessel wall simulating hydrogel compartment on release and distribution from model substance-coated stents. Four alginate-based gel formulations containing reversed-phase column microparticles LiChroprep® RP-18 or medium-chain triglycerides in form of preprocessed oil-in-water emulsions Lipofundin® MCT in different concentrations were successfully developed. Alginate and modified gels were characterized regarding the distribution coefficient for the fluorescent model substances, fluorescein and triamterene, and release as well as distribution of model substances from coated stents were investigated in the vFTC. Distribution coefficients for the hydrophobic model substance triamterene and the hydrophobized gel formulations were up to four times higher than for the reference gel. However, comparison of the obtained release profiles yielded no major differences in dissolution and distribution behavior for both fluorescent model substances (fluorescein, triamterene). Comparison of the test results with mathematically modeled data acquired using finite element methods demonstrated a good agreement between modeled data and experimental results indicating that gel hydrophobicity will only influence release in cases of fast releasing stent coatings.
KEY WORDSbiorelevant dissolution testing drug-eluting stent hydrophobized hydrogel release vessel-simulating flow-through cell
The authors thank Biotronik SE & Co. KG (Berlin, Germany) for supplying bare metal stent platforms. We are also grateful for the supply of Eudragit® by Evonik Industries AG (Essen, Germany). Additionally, the authors would like to acknowledge the laboratory work of Katja Semper, Marcus Schewe, and Thomas Brand. Furthermore, thanks are given to Grzegorz Garbacz for proposals regarding this work. This research was funded by the Federal Ministry of Education and Research (BMBF) within REMEDIS “Höhere Lebensqualität durch neuartige Mikroimplantate”.
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