Biomimetic apatite formed on cobalt-chromium alloy: A polymer-free carrier for drug eluting stent

[Display omitted] •Biomimetic apatite is formed on Co-Cr alloy as a polymer-free drug carrier.•To inhibit in-stent restenosis, sirolimus is loaded within apatite in two ways.•Porous and biodegradable biomimetic apatite releases of sirolimus over 40days.•Integrity of biomimetic apatite is sufficient for clamping and balloon expansion. In this study, sirolimus (SRL) was loaded within biomimetic apatite formed on cobalt-chromium (Co-Cr) alloy, which has been reported for the first time, to inhibit the in-stent restenosis. Two different groups of loading SRL within biomimetic apatite were prepared: Group A (mono-layer of apatite/SRL) and Group B (bi-layer of apatite/SRL). Group A and Group B showed the biphasic pattern of SRL release up to 40 and 90days, respectively. The attachment of human artery smooth muscle cell (HASMC) for both Group A and Group B was significantly inhibited, and proliferation dramatically decreased with the release of SRL. Noteworthily, biomimetic apatite alone also suppressed the SMC proliferation. The porous biomimetic apatite uniformly covered Co-Cr stent without crack or webbings. After balloon expansion, the integrity of biomimetic apatite was sufficient to resist delamination or destruction. Thus, this study demonstrated that biomimetic apatite is a promising drug carrier for potential use in stents.