Preparation and Evaluation of PDLLA/Sirolimus Coatings on Fully Bioabsorbable Drug-Eluting Stents

The objective of the this work was to prepare poly (D, L-lactide) (PDLLA)/sirolimus coatings on poly (L-lactide) PLLA stents by ultrasonic atomizing spray technology and to evaluate their morphology, mechanical property and in vitro drug release kinetic. Morphology and thickness of polymer/drug coating were observed by scanning electron microscopy (SEM) and the results show that the spray coating on stent surface was relatively homogeneous and smooth. Meanwhile, the mean roughness (Ra) of the coated stent surface was measured by atomic force microscopy (AFM) and results shows the mean roughness was 10.5 nm. There was no delamination or cracking of the coating in the crimping and balloon expansion process. It was found that the coating has ability to withstand large deformation. The sirolimus loading amount could be precisely controlled in this study. The optimization experiment of release media showed that sirolimus seemed to be relatively stable in PBS (PH 7.4) with SDS or Brij58 compared to other media. The in vitro release of sirolimus immersed in two optimized release media were analyzed by high performance liquid chromatography (HPLC). All the in vitro release profiles of sirolimus showed biphasic release characteristics with an initial burst period followed by sustained release. In terms of sirolimus release amount, release profiles shown that sirolimus release in PBS with Brij58 was superior to that in PBS with SDS and appeared slow-release in first two days in 0.1% Brij58 concentration which meets the requirement for clinical use.