Surface modification of titanium for load-bearing applications

Abstract

Titanium and its alloys are extensively used in load-bearing metallic devices. They are bioinert material and, therefore, get encapsulated after implantation into the living body by a fibrous tissue that isolates them from the surrounding tissues. Here we report modification of titanium surface using bioactive tricalcium phosphates (TCP) and nanoscale TiO2 to enhance cell-materials interaction. We have introduced bioactivity in Ti using laser-assisted coating of TCP and by anodization to grow surface TiO2 at room temperature using a mixed aqueous solution of sodium fluoride, citric acid and sulfuric acid as electrolyte. TCP coating showed a columnar Ti grains at the substrate side of the coating and transitioned to an equiaxed grains at the outside. Coating hardness increased from 882 +/- 67 to 1029 +/- 112 Hv as the volume fraction of TCP increased in the coating. For TiO2 nanotubes, microscopic analysis showed tubes of 50 nm in diameter with wall thickness of 15 nm and typical length between 200 nm and 1 micron based on anodization times. Effects of TCP and nanoscale TiO2 coating on bone cell-material interaction were examined by culturing osteoprecursor cells (OPC1) on coated surfaces. Antibacterial activity analysis using metallic Ag via electrodeposition showed over 99% antibacterial activity against the growth of colonies of Pseudomonas aeruginosa.