Identifier

etd-06262015-153612

Degree

Doctor of Philosophy (PhD)

Department

Engineering Science (Interdepartmental Program)

Document Type

Dissertation

Abstract

Bone tissue engineering approaches using polymer/ceramic composites show promise as effective biocompatible, absorbable, and osteoinductive materials. A novel class of in situ polymerizing thiol-acrylate based copolymers synthesized via an amine-catalyzed Michael addition was studied for its potential to be used in bone defect repair. Both pentaerythritol triacrylate-co-trimethylolpropane tris(3-mercaptopropionate) (PETA-co-TMPTMP) and PETA-co-TMPTMP with hydroxyapatite composites were fabricated in solid cast and foamed forms. These materials were characterized chemically and mechanically followed by an in vitro evaluation of the biocompatibility and chemical stability in conjunction with human adipose-derived mesenchymal pluripotent stem cells (hASC). The solid PETA-co-TMPTMP with and without hydroxyapatite (HA) exhibited compressive strength in the range of 7-20 MPa, while the cytotoxicity and biocompatibility results demonstrate higher metabolic activity of hASC on PETA-co-TMPTMP than on a polycaprolactone control. SEM imaging of hASC show expected spindle shaped morphology when adhered to copolymer. Micro-CT analysis indicates open cell interconnected pores. Foamed PETA-co-TMPTMP HA composite shows promise as an alternative to FDA-approved biopolymers for bone tissue engineering applications. The results of the six week in vivo biocompatibility study using a posterior lumbar spinal fusion model demonstrate that PETA:HA can be foamed in vivo without serious adverse effects at the surgical site. Additionally, it was demonstrated that cells migrate into the interconnected pore volume are found within centers of ossification. Because the natural mechanical strength of materials is highly dependent on the crystal structure, four different silicate-derived ceramics—diopside, akermanite, monticellite, and merwinite have been synthesized and evaluated for their potential as bone augments and grafts. This sparks our interest in the fabrication of polycaprolactone (PCL)/ceramic composites for potential use as scaffolds. Akermanite and monticellite exhibit better osteogenic properties than diopside and merwinite, suggesting that they might be the optimal material for fabricating bone scaffolds.

Date

2015

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Hayes, Daniel

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