Cross-linking Methods for 3D Printable Hydrogel Materials

Abstract

Stimuli-responsive hydrogels have gained increased attention for a broad range of biomedical and biotechnological applications. Synthetic polymeric systems are an attractive platform as they afford tunability through the control of monomer side-chains and block composition. Additive manufacturing, as a versatile method of fabrication, is widely used in bioprinting however, the range of functional materials is limited. This dissertation describes the research on the design and development of novel polymer hydrogels and the characterization of rheological characteristics to enable extrusion-based additive manufacturing applications. Chapter 1 is an introduction to additive manufacturing and stimuli-responsive polymeric hydrogels. The study of Chapter 2 represents our work on developing a novel cross-linkable hydrogel based on alkyl glycidyl ether monomers. The resulting gel has tunable stiffness based on photoinitiator concentration and UV irradiation length. Chapter 3 focuses on the exploration of telechelic functionalization of F127 to modify the gelation temperature and rheology. The only modifications that resulted in a noticeable change were the addition of a urea spacer and formulation of boronic acid chain-ends with galactose functionalized F127 or curdlan polysaccharide. The work of Chapter 4 discusses the influence a water-soluble dithiol has on the competition between chain-extension and polymerization on a methacrylated F127 hydrogel. When the dithiol is formulated in excess, slow thiol-ene occurs over the course of days to increase the molecular weight of F127 chains before UV cure. Careful control of equilibration prior to UV cure affords a gel that is stretchable and suturable when extruded through a coaxial nozzle.