Characterization of drug-eluting stent (DES) materials with cluster secondary ion mass spectrometry (SIMS)

Secondary ion mass spectrometry (SIMS) employing an SF5+ polyatomic primary ion source was utilized to analyze several materials commonly used in drug-eluting stents (DES). Poly(ethylene-co-vinyl acetate) (PEVA), poly(lactic-co-glycolic acid) (PLGA) and various poly(urethanes) were successfully depth profiled using SF5+ bombardment. The resultant molecular depth profiles obtained from these polymeric films showed very little degradation in molecular signal as a function of increasing SF5+ primary ion dose when experiments were performed at low temperatures (signal was maintained for doses up to ∼5 × 1015 ions/cm2). Temperature was determined to be an important parameter in both the success of the depth profiles and the mass spectral analysis of the polymers. In addition to the pristine polymer films, paclitaxel (drug released in Taxus™ stent) containing PLGA films were also characterized, where it was confirmed that both drug and polymer signals could be monitored as a function of depth at lower paclitaxel concentrations (10 wt%).