Multifunctional Ti-xCu coatings for cardiovascular interfaces: Control of microstructure and surface chemistry

Ti-xCu coatings with varied Cu contents were deposited by hybrid HiPIMS/DC magnetron co-sputtering to achieve optimum microstructures and surface chemistries for applications as multi-functional, blood-contacting interfaces. We have demonstrated that control over the chemistry and microstructure of the coatings provides interfaces that simultaneously exhibit antibacterial properties, show endothelial cell (EC) compatibility, and prevent smooth muscle cell (SMC) proliferation. Using XRD and HRTEM analyses, we identified distinct microstructures for coatings with various Cu/(Cu + Ti) atomic concentrations. The corrosion resistance was controlled by the microstructure of the Ti-xCu coatings and decreased with increases in the Cu atomic concentration. XPS and ICP-MS results provided evidence that copper ions are released from the coatings upon immersion in PBS solution. We have demonstrated that the Cu-containing phases are weak points that are attacked and corroded easily, resulting in the release of Cu ions from the coatings. The coatings with Cu/(Ti + Cu) ratios ranging from 3 to 65 at.% inhibited the viability of SMCs significantly. The optimized coating with Ti and Cu/CuTi_x crystals and Cu/(Ti + Cu) ratio of 16 at.% showed significant improvements in EC compatibility as well as reduced viability of SMCs, holding great promise for the surface modification of cardiovascular devices such as stents and coronary implants. The coatings with amorphous phases and Cu/(Ti + Cu) ratios of 55 and 65 at.% showed excellent antibacterial properties against Staphylococcus aureus bacteria. The coating with 55.0 at.% Cu is an encouraging material for the surface engineering of blood-contacting implant surfaces that have antibacterial properties but are not cytotoxic to SMCs.