3D-additive deposition of an antibacterial and osteogenic silicon nitride coating on orthopaedic titanium substrate.

A 3D-additive manufacturing approach produced a dense SiN ceramic coating on a biomedical grade commercially pure titanium (cp-Ti) substrate by an automatic laser-sintering procedure. SiN coatings could be prepared with thicknesses from the single to the tens of microns. A coating thickness, t = 15 ± 5 μm, was selected for this study, based on projections of homogeneity and scratching resistance. The SiN coating met the 20 N threshold required for biomaterial applications, according to the standard scratch testing (ASTM C1624-05). The SiN coating imparted both the antibacterial and osteogenic properties of bulk SiN to the cp-Ti substrate. Both properties were comparable to those previously described for bulk SiN biomedical implants. The newly developed SiN-coating was applied to commercially available Ti-alloy acetabular shells for total hip arthroplasty. A "glowing" test based on luciferase gene transformation was applied to visualize the colonization of gram-negative Escherichia coli on SiN-coated and uncoated Ti-alloy acetabular shells. The results showed that the coating technology conferred resistance to Staphylococcus epidermidis and Escherichia coli adhesion onto the bulk acetabular sockets.