Date of Award

2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering–Engineering Mechanics (PhD)

College, School or Department Name

Department of Mechanical Engineering-Engineering Mechanics

Advisor

Tolou Shokuhfar

Co-Advisor

Cortino Sukotjo

Abstract

Titanium and its alloys are typically used for fabrication of dental and orthopedic implants as they possess various desirable properties including biocompatibility and corrosion resistance. In spite of such benefits, titanium implants show lack of osseointegration after surgery in minor cases. The objective of this research has been to modify the surface of titanium alloy for medical applications through increasing surface hydrophilicity and drug loading. Primarily, anodization method is employed for fabrication of nanotubes on titanium surface to act as anchoring cite for cells.

Considering the key role of surface hydrophilicity on cellular attachment to the surface and subsequent biological behavior of attached cells, the fabrication condition of nanotubes during anodization and following heat treatment is optimized. It is shown that anodization voltage, anodization duration and heat treatment temperature and duration can be controlled to fabricate a nanotubular surface that maintains its hydrophilicity over a long period of time. In order to verify the role of surface morphology on obtained characteristics, smooth, anodized-smooth, rough and anodized-rough surfaces are explored. The results show that anodized-smooth and anodized-rough surfaces show higher hydrophilicity than non anodized surfaces. Hydrophilic nanotubes not only promote cell adsorption; but also increase absorption of aqueous drug solution. Consequently, nanotubes are successfully loaded with drug and act as nano drug reservoirs that are potential to deliver the loaded drug locally after surgery. It is shown that dimension of nanotubes can affect rate of drug release. In fact the results indicate that nanotubes with higher aspect ratio (ratio of length to diameter) prolong drug release. A novel method for fabrication of naotubes was investigated which suggests a new way for controlling length of nanotubes. It is shown that heat treatment of the substrate prior to anodization affects length of nanotubes obtained eventually after anodization. In fact, the results show that anatase crystalline structure affects mechanism of formation of nanotubes to form longer nanotubes. Finally, it is demonstrated that corrosion resistance of heat treated nanotubular surface is higher than either heat treated surface or nanotubular surface alone.

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