Improvements of Blood Compatibility, Drug-in-Polymer Coating Stability and Prevention of Crack Formation: Application to Drug-Eluting Stents

Commercially available drug-eluting stents still suffer from poor blood compatibility, polymer coating delamination, cracking and lack of stability during and after stent implantation that led to adverse events such as stent thrombosis and in-stent restenosis. This article highlights the advantages of using silicon nanofilament (SiNf) as an interface between stent surface and drug-in-polymer coating or bloodstream. The SiNf was successfully formed on the surface of Co-Cr substrate via one-step simple method. The morphology of the filaments showed nanosized structures with nano-gaps between the filaments. After coating the nanofilaments with a mixture of sirolimus and poly(D,L-lactide), an interlocking mechanism was established in which the coating penetrates the nano-gapes between the filaments. Therefore, the presence of SiNf enhanced the coating stability with no coating delamination whereas, the control substrate presented 97% of coating delamination. For stent application, the SRL-in-PDLLA matrix was coated on stent platform with smooth and uniform morphology without webbing between stent struts. After stent ballooning, the control stent presented cracking and peeling of the polymer coating from the surface whereas, the SiNf-modified stent did not show any sign of these unfavorable defects. Moreover, the platelet adhesion on the SiNf surface showed a lower number with round shape morphology compared to control Co-Cr. This suggests that modifying the substrates with SiNf could act as a universal coating for reinforcing the polymer coating stability, prevent coating defects that accompany stent ballooning, and improve the blood compatibility of the material surfaces that could have various applications to medical implants and devices.