Biomimetic Extracellular Matrices for In Vitro Cancer Models and Tissue Engineering Platforms

This thesis describes approaches to resolve inadequacies with current hydrogels used for cancer models and tissue engineering platforms, namely, (i) overcoming light scattering in nanofibrillar hydrogels, (ii) independently controlling matrix stiffness from other matrix properties, and (iii) generating structurally anisotropic networks. As nanofibrillar hydrogels scatter light and strongly interfere with the optical characterization of cells, the first project describes the development of a temperature-responsive nanofibrillar hydrogel for the on-demand release of encapsulated cancer spheroids to enable optical, cellular, and molecular characterization of cells. Using a suspension of cellulose nanocrystals functionalized with temperature-responsive polymer molecules, a filamentous hydrogel was formed at 37 degrees Celsius that supported the growth of cancer spheroids. Upon hydrogel cooling to room temperature, on-demand release of cancer spheroids without loss of cell viability and spheroid integrity was achieved. In the second project, I designed a fibrillar hydrogel with the mechanical properties controlled independently of pore size, polymer composition, and cell ligand adhesion density for the evaluation of matrix stiffness on the response of cancer spheroids to a chemotherapeutic drug. A twenty-fold variation in stiffness of the hydrogel was achieved. At sufficiently long culture times (when the matrix stiffness influenced spheroid growth), the growth of larger cancer spheroids with a lower fraction of proliferating cells occurred in softer gels. These spheroids showed stronger resistance to anticancer drug, doxorubicin. In the third project, I fabricated structurally anisotropic hydrogel sheets using extrusion-based 3D printing of a temperature-responsive and shear-thinning ink composed of cellulose nanocrystal methacrylate (CNC-MA) and gelatin methacrylate (Gel-MA). The shear-induced alignment of CNC-MA was preserved by cooling and photocrosslinking of the extruded hydrogel sheets. The degree of structural anisotropy was controlled by varying the cooling temperature of the stage onto which the gel was extruded and the volumetric flow rate of the ink. The extruded hydrogel sheets exhibited anisotropic mechanical and swelling properties. In the fourth project, I generated biocompatible hydrogel sheets composed of regions with different degrees of anisotropy. I used an aldehyde-modified cellulose nanofibril and gelatin mixture for the extrusion-based 3D printing of hydrogel sheets with alternating structurally anisotropic and isotropic regions. Human dermal fibroblasts cultured on the extruded hydrogels showed oriented growth.

Department dc:contributor.department

Chemistry

Year dc:date.issued

2021

Author dc:creator

• Khuu, Nancy

Advisor dc:contributor.advisor

• Kumacheva, Eugenia

Handle dc:identifier.uri

http://hdl.handle.net/1807/109210

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/109210