All ETDs from UAB

Advisory Committee Chair

Susan L Bellis

Advisory Committee Members

Yogesh K Vohra

Xu Feng

Jack E Lemons

Timothy M Wick

Document Type


Date of Award


Degree Name by School

Doctor of Philosophy (PhD) School of Engineering


Orthopaedic implants fail when bone loss around the anchoring region of the prosthesis causes the components to loosen. A revision surgery is needed to replace worn components, and bone grafting is often required to fill the void caused by osteolysis. A solution for the problem of osteolysis may be the improvement of wear resistance at the articulating surfaces by substituting materials with greater hardness. This dissertation describes two strategies for increasing the surface hardness of titanium alloy (Ti-6Al-4V) implants, without increasing surface roughness or compromising osseointegration. The first strategy utilizes microwave plasma to induce titanium nitride formation by nitrogen diffusion. The result is a gradual transition from a titanium nitride surface to the bulk titanium alloy, without a sharp interface that could otherwise lead to delamination. The second strategy employs a layer of nanostructured diamond on the surface of the implant, resulting in a surface hardness 14-fold that of Ti-6Al-4V and 7-fold greater than cobalt alloy. The interaction of human mesenchymal stem cells (MSCs) with both new biomaterials was found to be at least as favorable as CoCrMo, and often as favorable as Ti- 6Al-4V. In addition, hydrogen (H) - terminated USND surfaces supported robust MSC adhesion and survival, while oxygen (O) and fluorine (F) -terminated surfaces resisted cell adhesion, indicating that USND can be modified to either promote or prevent cell/biomaterial interactions. iii The third aim of this dissertation included the development of new biodegradable scaffolding products that encourage bone regeneration. The scaffolds are nanofibrous composites composed of collagen, hydroxyapatite, and polycaprolactone, produced by the technique of electrospinning. We demonstrated that incorporation of a small amount of collagen I fibers is beneficial, although 100% collagen electrospun fibers are a poor substrate for MSCs. Evidence is also presented that incorporation of hydroxyapatite nanoparticles into the scaffolds is also beneficial for increasing MSC density. While these three biomaterials potentially have a broad range of applications, they were developed specifically for improving the outcome of joint replacement surgeries. These findings underscore the importance of careful design of surface chemistry, surface topography, and mechanical properties in the design of biomedical implants.

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