Synthesis and characterization of elastic star shape-memory polymers as self-expandable drug-eluting stents

Elastic shape-memory polymers as self-expendable polymeric drug-eluting stents are developed for the first time, with good mechanical properties, fast self-expansion, and sustained drug release. Novel star block co-polymer PCTOPDs containing hyperbranched poly(ε-caprolactone) (PCL) switching segment and poly(2-oxepane-1,5-dione) (POPD) hard segment were synthesized in high yield and characterized by NMR, GPC, DSC, tensile test and cyclic thermomechanical tensile test. PCTOPD containing 15–27 wt% POPD (PCTOPD-15–27) are found to be non-cytotoxic thermoplastic elastomers (Tm of 39–40 and 120–129 °C, εb of 908–1060%, σm of 12–20 MPa, and E of 60–91 MPa) with good shape-memory properties at 40 °C (Rf of 95–97%, Rr of 97–99%, and shape recovery time of 35 s). The stent made from PCTOPD-27 gives nearly full self-expansion at 37 °C within 45 s. The collapse pressure at a compressive strain of 30% is 1.7 bar. A stent containing 3.0 wt% paclitaxel releases 42% drug linearly in the first 9 days and 67% drug in 30 days with a slower but nearly linear release for the period of 10–30 days. The developed SMP-based drug-eluting stents might be useful in biomedical application such as the treatment of coronary artery disease.