Study On The Drug Release And Radical Force Of Drug-eluting Stents

Recently the application of rapamycin drug-eluting stents (DES) in the coronaryartery intervention treatment gradually increased. However, the related features of thedrug-eluting stent, such as ingredient analysis, release rate in vitro and in vivocorrelation and radial force research is still unclear. Herein, the stent coatingZotarolimus manufactured by Medtronic was used in this experiment. The mainresults as follows:Firstly, HPLC method was applied for qualitative and quantitative analysis of therelease rate of the Zotarolimus drug-eluting stents in vitro. After assaying systemticapplicability and method suitability, the qualitative and quantitative test method wasestablished. The results of analysis of three types of stents demonstrate that thismethod is simple operation with good reproducibility and stability. Meanwhile, theapproach, which is carried out with1%solutol1:1at100rpm and37.0℃, was set upto investigate the release rate of drugs coating the stent in vitro. The release processesdisplayed a rapid release at the early stage and a gently release at the late stage, whichis consistent with the normal release trends of ustained-release in vitro. Taken together,above results provide the technical support for guaranteeing the product quality ofdrug-eluting stents.Secondly, the three-month old miniature pigs (25kg～35kg) were selected tocarry out the animals test. The stent was delivered through the right coronary artery.Afterwards, to explore the release of drug from the eluting stents in vivo, the stentswere taken out from blood vessels at predetermined time and flushed with phosphatebuffer solution for test. Almost all the drugs can be released from stents in10days,the release drug in the first day is the most, which accounts for70%of total drugcoating on the drug-eluting stents. The release curve have undergone a rapid release atthe early stage and gently release at the late stage, which confirms to meet with therelease trend of the sustained-release preparations in vitro. This procedure completelymeets the clinical requirement.Additionally, A-class modeling method was used to explore the releasecorrelation of in vivo and in vitro. The release curve in vitro correspond to each pointin vivo has a linear regression, the in vivo time (days)=3.42*in vitro time (h)-0.367. So the correlation in vitro can predict the change of drug absorption in vivo.Finally, the radial force of the stents with different diameters and differentwelding processs was investigated with the radial strength tester. The resultsdemonstrated that the welding process directly impacted the radial force, while thechange of the radial force isn’t related to the stent diameter.