Cardio-vascular stents with cell-repellent micro- and nanostructures generated by fs laser processing

We describe the formation of fs-laser induced micro- and nanostructures for cell-repellence on Co-alloy based cardio-vascular stents. Under investigation were fibroblast cells, a cell type which is important for re-occlusion of blood vessels with implanted stents. For comparison, the behavior of endothelial cells on the laser-treated material was also investigated, as those form the natural inner surface of blood vessels. The inflated stents were exposed to the beam of a 1040 nm Yb-based amplified fs laser system with a pulse length of about 300 fs. The laser exposure results in a surface topography with micro-spikes covered by oriented nano-ripples (i.e., laser-induced periodic surface structures, LIPSS). Laser irradiation was performed either directly through the wire mesh or exclusively from the inside of the stent using faceted quartz rods that functioned as waveguides. In the latter case, the laser beam was deflected by about 30° or by 90° depending on the facet angle. This was achieved by polishing a quartz tube with a diameter corresponding to the inner diameter of the inflated stent. Cell growth on these substrates was inspected after a cultivation period of 4 to 10 days by means of scanning electron microscopy. In a proof-of-principle, we show that the micro- and nanostructures have a cell-repellent effect, especially for fibroblasts. This method may provide a basis to produce cell-repellent stents, in future.