Electrospun hydroxyapatite-containing chitosan nanofibers crosslinked with genipin for bone tissue engineering applications

Michael E. Frohbergh

doi:10.17918/etd-4058

Reconstruction of large bone defects remains problematic in orthopedic and craniofacial clinical practice. Engineering a functional scaffold mimicking the architectural structure of bone and the regenerative capacity of periosteum offers a potential solution. Electrospun nanofibrous scaffolds are superior in surface area, biomimetic properties, and architecture for the proliferation, and differentiation of osteoprogenitor cells. Chitosan (CTS), the deacetylated form of chitin found in the exoskeleton of crustaceans, is a versatile biomaterial with structural similarity to the extracellular matrix (ECM) of bone. In this thesis, the need of fabricating a regenerative material for bone tissue engineering is addressed by demonstrating the ability of genipin crosslinked electrospun chitosan (CTS-GP) nanofibers mineralized with hydroxyapatite (CTS-HA-GP) to act as osteogenic templates capable of supporting osteoblast adhesion and differentiation with the potential to induce mesenchymal stem cell differentiation and craniofacial regeneration in vivo. Fibrous scaffolds with average fiber diameters of 227±154 nm as spun and 335±119 nm after crosslinking with genipin were generated. Physical, chemical and mechanical analyses were performed for scaffold characterization as well as cytocompatability and osteogenic expression of 7F2 mouse osteoblasts to demonstrate the ability of these scaffolds to support functional osteoblasts. Induction was also observed by the capacity of these scaffolds to induce osteogenic differentiation of human bone-marrow derived mesenchymal stem cells in vitro. Finally, the osseointegrative capacity of these scaffolds was observed by in vivo implantation into a murine calvarial defect model, demonstrating no immunorejection and the early presence of calcified tissue formation. Furthermore the need for enhanced porosity in electrospun scaffolds to induce proper cell infiltration into the scaffold using mesenchymal stem cells on PLGA scaffolds with sacrificed gelatin fibers was also explored. PLGA was used to look into optimizing an appropriate scaffold for bone regeneration due to its ease in fabrication and manipulation by observing mechanical properties and porosity at different ratios compared with cell infiltration. However, it was observed that the gelatin was not being removed as hypothesized and was rather modifying the physical properties of the scaffold. A mathematical model was developed to describe cell proliferation across the scaffolds and cell infiltration into the scaffold.

Electrospun hydroxyapatite-containing chitosan nanofibers crosslinked with genipin for bone tissue engineering applications

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Electrospun hydroxyapatite-containing chitosan nanofibers crosslinked with genipin for bone tissue engineering applications

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