This thesis investigates new processing methods and bone tissue engineering applications of cross-linked cellulose nanocrystal (CNC) aerogels. Aerogels are highly porous, low-density materials that have been praised for their high surface area and interconnected pores, but criticized for their brittleness. This prompted a search for new aerogel “building blocks” to produce more flexible materials; CNCs meet this need and chemically cross-linked CNC aerogels have good compressive strength and shape recovery properties in air and liquid environments.
CNCs are high aspect ratio, non-toxic and renewably-sourced nanoparticles. Literature has demonstrated CNC aerogel production using cryo-templating with controlled drying. In this work, we produce aerogels using a new scalable process called pressurized gas expansion (PGX) and compare them to conventional cryo-templated aerogels. PGX aerogels were found to have more expanded fibrillar morphology, a range of mesopore sizes and smaller macropores, in contrast to cryo-templated aerogels that had a sheet-like morphology surrounding larger macropores. Additionally, PGX aerogels had higher specific surface area and porosity, but lower compressive strength due to a lower cross-link density. While neither CNC aerogel type dispersed in water, PGX aerogels partially shrank whereas cryo-templated aerogels did not; this is attributed to their morphological differences. This work shows that new aerogel processing methods can introduce new properties and thus broaden the potential applications of CNC aerogels.
One specific biomedical application was evaluated for CNC aerogels – their use as bone tissue scaffolds. Cryo-templated aerogels comprised of CNCs with different surface chemistries, either sulfate or phosphate groups, were found to have attractive chemical, physical and mechanical properties for bone tissue engineering. This work shows that both types of CNC aerogels can facilitate cell proliferation, favorable differentiation, and can nucleate uniform hydroxyapatite growth. These positive in vitro results and the bimodal pore morphology of CNC aerogels make them promising bone scaffolds for in vivo studies. / Thesis / Master of Applied Science (MASc) / Aerogels are light, porous, sponge-like materials that are essentially 99% air by volume. In this work, the aerogels are made from non-toxic plant-based nanoparticles called cellulose nanocrystals (CNCs). This thesis investigates: 1) new ways to control CNC aerogel properties and pore size through different processing methods and 2) the use of CNC aerogels to aid in the repair of damaged bones. High-resolution microscopy and nano-characterization tools show that CNC aerogels have tunable properties, which may extend their possible applications. The internal structure, sponge-like mechanical properties and biocompatibility of CNC aerogels allowed them to be successfully utilized to support bone cells and grow bone-like mineral.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/22243 |
| Date | 11 1900 |
| Creators | Osorio, Daniel |
| Contributors | Grandfield, Kathryn, Cranston, Emily, Materials Science and Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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