In vitro Biocompatibility Analyses of Stents Coated with Diamond-Like Carbon by Flow Cytometry, Cell Growth Assays and Electron Microscopy

Background: Coronary artery stents can induce platelet activation by shear forces and contact to the biomaterial. This activation is one important trigger for thrombosis. Coating of stents is a possible approach to prevent this side effect. The purpose of this study was to evaluate in vitro the biocompatibility of stents coated with diamond-like carbon (DLC). Materials and Methods: For in vitro testing, DLC-coated stents were compared with noncoated 316L stainless steel stents. For this purpose, cell culture assays, videomorphometric, electron microscopic and flow-cytometric techniques were applied. Results: Growth assays with smooth muscle cells and endothelial cells revealed that DLC did not affect proliferation rates and did not have cytotoxic effects. Video-based morphometry and scanning electron microscopy showed an ultrasmooth surface and homogenous expansion patterns of the DLC stents. For analysis of platelet antigens in a circulating loop model, flow cytometry was applied. Our experiments showed no significant changes in mean channel fluorescence intensity for the structural antigens CD41a (p = 0.6) and CD42b (p = 0.1). In contrast, the expression of the activation-dependent antigens CD62p and CD63 increased significantly in noncoated stents compared to DLC-coated stents (p < 0.05). Conclusion: Coating of intracoronary stents with DLC significantly reduces platelet activation. Hereby, biocompatibility is improved.