Nanostructured metal surfaces by plasma immersion ion implantation

For bare metal stents the in-stent restenosis was a serious problem for about 25 - 35% of the patients and this spurred the medical device companies to come up with a solution. Drug-eluting stents are designed to deliver a drug locally from a polymeric coating to reduce tissue in growth and reduce restenosis to less then 8% of the treated patients. Development of novel materials and structures for drug delivery systems is still very actual topic.
In the present work plasma immersion ion implantation (PIII) using helium or argon plasmas has been employed for the nanostructures formation on metal surfaces with a view to their applications for metal-based drug-eluting stents. A multi-layer pore system on stent surfaces in the range from nanoscale to microscale sizes is desired for drug loading and controlling the rate of elution of therapeutic agents.
Recently we have investigate the formation of nanostructures on stainless steel surfaces by PIII at different gases (He, Ar), ion energies (between 5 – 35 keV) and ion fluences (> 1e18 at/cm2). The surface topography and structure of the implanted materials were analysed by scanning electron microscopy and atomic force microscopy. The phase and element compositions were examined by grazing incidence X-ray diffraction analysis, auger electron spectroscopy, and elastic recoil detection analysis.
Variety of nanostructures as well as their characteristics (e.g. size, distribution, degree of interconnection) can be controlled by varying the implantation parameters. The results of these studies have demonstrated that PIII is a promising technique for the surface topography modification of stainless steel for cardiovascular application.