Bioengineering cobalt chromium cardiovascular stent biomaterial for surface enhancement and characterization

Cobalt Chromium alloy L605 is an underlying biomaterial for most new generation drug eluting stents (DES) and bare metal stents (BMS). Suboptimal biocompatibility of stents clinically manifest as thrombosis and restenosis. We optimized a plasma-activated coating (PAC) technology to modify alloy L605 material surface (PAC-L605), for the first time, for enhanced biocompatibility. This study details in vitro characterization to identify and optimize the physical, chemical, and mechanical properties of the modified material surface PAC-L605. Surface hydrophilicity characterized post-modification with water contact angle and plasma kinetics, showed improved hydrophilicity for PAC-L605. Surface chemistry of PAC-L605 vs. L605, quantified with energy dispersive x-ray spectroscopy (EDS), showed comparatively higher percent weight of carbon and nitrogen on PAC surfaces. The microscale, isotropic surface roughness of PAC-L605, was computed with NanoMap white light interferometry (WLI). Surface stiffness computed via nanoindentation at minimum compression load 0.19 mN - increasing to maximum load 50 mN, showed similar stiffness for PAC- L605 and L605 at higher load. Nanoindentation results confirmed robust adhesion of PAC to L605, and unique non-delaminating character of PAC under compression. Furthermore, surface modification at PAC-L605 interface was visualized via high-resolution transmission electron microscopy (HRTEM). Improvements of surface character for implantable cardiovascular materials could be achieved by plasma-activated coating (PAC). Optimal surface modifications may trigger desirable biological responses in vitro and in vivo . 1