Representative SEM images of clinically tested porous stents. (a-i) Microporous
hydroxyapatite-coated stent filled with sirolimus formulation (a-ii) cross section of
the nanothin hydroxyapatite coating (∼600 nm). Reprinted with permission from Costa
et al., JACC: Cardiovasc. Interventions 2(5), 422–427
(2008). Copyright 2008, Elsevier. (b-i) Nano+TM polymer-free stent showing
strut microstructure after expansion. Strut thickness is approximately 91
μm having a large number of sirolimus-filled pores (∼400 nm) on the
abluminal stent surface. (b-ii) Electron microscopy images of the nanopores
(magnification ×20 000). Reprinted with permission from Liu et al.,
Catheterization Cardiovasc. Interventions 95(S1), 658–664 (2020). Copyright
2020 John Wiley and Sons.