It is predicted that the percentage of persons over 50 years of age affected by bone diseases will double by 2020 (Navarro et al., 2008). Clearly this represents a need for permanent, temporary or biodegradable orthopaedic devices that are designed to substitute or guide bone repair. Polymeric medical devices are widely used in orthopaedic surgery and play a key role in fracture fixation and in areas of orthopaedic implant design. Initial uncertainty regarding the adequacy of polymeric materials to withstand functional stresses obliged clinicians to implement these biomaterials in non-load-bearing applications such as fixation of the maxillofacial skeleton. Strategies to guide bone repair, have included topographical modification of these devices in an attempt to regulate cellular adhesion, a process fundamental in the initiation of osteoinduction and osteogenesis. Advances in fabrication techniques have evolved the field of surface modification and, in particular, nanotechnology has allowed the development of experimental nanoscale substrates for the investigation into cell-nanofeature interactions. This thesis is concerned with the study of nanotopographical structures on osteoblast adhesion and mesenchymal stem cell (MSC) function, with an aim to improving the functionality of orthopaedic craniomaxillofacial devices. In this study primary human osteoblast (HOBs) were cultured on nanoscale topographies fabricated by lithographic and phase separation techniques in poly(methyl methacrylate) (pMMA). Adhesion subtypes in HOBs were quantified by immunofluorescent microscopy and cell-substrate interactions investigated via immunocytochemistry with scanning electron microscopy. To investigate the effects of these substrates on cellular function 1.7 K microarray analysis was employed to study the changes in gene profiles of enriched MSC populations cultured on these nanotopographies. Nanotopography differentially affected the formation of adhesions in HOBs and induced significant changes in genetic expression of MSCs on experimental substrates. Nanopit type topographies fabricated by electron beam lithography were shown to inhibit directly the formation of large adhesion complexes in HOBs and induce significant down-regulation of canonical signalling and functional pathways in MSCs. Nanocrater and nanoisland type topographies fabricated by polymer demixing however reduced adhesion formation and induced up-regulation of osteospecific pathways. Nanogrooved topographies fabricated by photolithography influenced HOB adhesion formation and MSC osteospecific function in a manner dependant on the groove width. The findings of this study indicate that nanotopographical modification significantly modulates both osteoblast adhesion and MSC function, implicating topographical modification as a viable strategy to enhance orthopaedic device functionality.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:495144 |
| Date | January 2009 |
| Creators | Biggs, Manus Jonathan Paul |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/552/ |
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