Enhancing biocompatibility of tantalum via anodization for orthopedic applications

Uslu, Ece
Ercan, Batur
Tantalum and its alloys have been investigated as the next generation of orthopedic implant materials in the last decade. Being a valve metal, tantalum forms a naturally occurring stable oxide layer approximately 3-5 nm on its surface at ambient conditions and this layer both prevents heavy ion release from the metal and provides a natural barrier for implant corrosion. In fact, due to its chemically inert nature, tantalum has the highest corrosion resistance of all metals used in orthopedic applications. Tantalum also exhibits higher fatigue properties compared to the currently-used implant materials. Despite having ideal properties for orthopedic applications, bioinert nature of tantalum surfaces, which limits osseointegration with the juxtaposed tissue, is the leading problem to be addressed before its widespread use in implants. To overcome this problem, surface modification of tantalum within nanoscale could be a potential remedy to enhance its bioactivity. Anodization is an electrochemical process which produces oxide based nanofeatured surfaces on various metals. It gained popularity in the last decade due to its versatility in controlling biomaterial surface topography. In literature, it was shown that anodized nanostructured surfaces having different morphologies, topographies and feature sizes enhanced bone cell adhesion, proliferation and cellular functions in orthopedic applications. Specifically, anodized titanium and its alloys were well characterized to enhance cellular functions in vitro. However, there is very limited data on the anodization of tantalum for orthopedic applications. In this study, tantalum samples were anodized using 1M H2SO4+ 3.3 wt % NH4F, 1:9 (v/v) concentrated and aqueous HF/H2SO4 solutions to obtain oxide based nanofeatures on its surface. Upon anodization, 4 different surface morphologies, namely nanodimple, nanotubular, nanoporous and nanocoral, were successfully obtained on tantalum surfaces. Furthermore, anodization duration (1min-4hr) and voltages (10-80V) were fine-tuned to control feature sizes between 25 to 140 nm for the nanodimple, nanocoral and nanoporous morphologies. Topographical investigations indicated higher nanophase surface roughness on anodized surfaces compared to as-received tantalum. Anodized samples also expressed enhanced surface hydrophilicity independent of the morphology and feature size. To investigate biocompatibility of the samples, osteoblast (ATCC CRL-11372) adhesion and proliferation were examined up to 7 days of culture. Results indicated enhanced cellular functions on nanodimple, nanocoral and nanoporous morphologies compared to non-anodized surfaces. Furthermore, immersing these samples into simulated body fluid up to 1 month showed enhanced bioactivity of these surfaces compared to nonanodized tantalum. In conclusion, surface modification of tantalum via anodization could be a potential way to enhance biocompatibility of tantalum for orthopedic applications
Citation Formats
E. Uslu and B. Ercan, “Enhancing biocompatibility of tantalum via anodization for orthopedic applications,” presented at the MRS Fall Meeting and Exhibit, November 25-30 2018, Boston, Massachusetts, USA, 2018, Accessed: 00, 2021. [Online]. Available: https://hdl.handle.net/11511/88039.