Nanoscaffolds in Ti Alloys to Enhance Osseointegration

University Of Puerto Rico Mayaguez, Mayaguez PR

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Abstract

Two concerns have been raised with respect to the long-term stability of the bone-metal interface in hard tissue implants. Firstly, failure occurs at the interface due to a lack of proper osseointegration. The second concern is the failure of the oxide or hydroxyapatite (HAP) coating because of its brittle nature. Since the goal is to increase implant longevity, efforts must be made to enhance osseointegration considerably. The proposed concept for strengthening this bone-metal interface js the creation of nanoscaffolds by in situ oxidation and functionally layered (FL) oxide/HAP coatings to force chemical bonding rather than mechanical keying effect alone. This is expected to greatly strengthen the bone-metal interface which, in turn, will increase implant longevity. In the first phase of this proposal, simple in situ oxidation of commercially pure (cp) titanium, Ti-6AI-4V and Ti-48AI-2Cr-2Nb (at.%) will be carried out at 500 [unreadable]C and 800 [unreadable]C to create oxide nanoscaffolds, which will also be characterized. Cytocompatibility and cell attachment in these modified materials will be researched using human fetal osteoblasts. Wear properties of these surfaces will also be studied in a biological fluid environment. In the second phase, a thin coating of HAP will be added on to the nanoscaffolds to create FL surfaces with the goal of further enhancing osseointegration. The final phase involves the use of a rabbit model to implant these modified materials carrying the nanoscaffolds in the femur, followed by push out tests to determine quantitatively the degree of osseointegration to practically determine the utility and effectiveness of the proposed method using nanoscaffolds. The hypothesis behind this proposal is that the nanoscale structure "seen" by the bone cells will encourage them to effectively deposit collagen and bone mineral at this scale because of size similarity. The oxide/FL nanoscaffolds will encourage and strengthen chemical bonding at the fundamental level to enhance osseointegration. This is expected to enhance implant longevity in knee and hip arthroplasty for all patients. The results of the study will be especially useful for younger more active patients to provide them with a better quality of life.