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UBC Theses and Dissertations

Constructing hydrogels from engineered protein Kong, Na


Hydrogels are crosslinked polymer networks that absorb large amounts of aqueous solutions. The varieties of hydrogel building blocks include natural polymers, synthetic polymers and genetically engineered proteins. This dissertation will discuss the latest progress of hydrogels constructed from genetically engineered proteins (recombinant proteins), mainly focusing on biorecognition-driven physical hydrogels as well as chemically crosslinked hydrogels. Examples include dynamic hydrogels and designing hydrogels via protein fragments reconstitution. The first class of studies presented in this dissertation involves the use of molecular level processes to control macroscopic mechanical properties. A novel protein hydrogel is reported showing dynamic mechanical properties based on a redox potential controlled protein folding-unfolding switch, which is constructed from a designed mutually exclusive protein. The changes of the mechanical and physical properties of this hydrogel are fully reversible and can be applied as extracellular matrix to investigate cell response upon varying stiffness. In addition, another powerful method, metal chelation, is reported to tune the conformational change of mutually exclusive protein, which can stabilize the domain, initiate the folding switch and further affect the mechanical properties of resultant hydrogel. In the second class of studies, protein fragment reconstitution has been demonstrated as a novel driving force for engineering self-assembling reversible protein hydrogels. Protein fragment reconstitution, also known as fragment complementation, is a self-assembling mechanism by which protein fragments can reconstitute the folded conformation of the native protein when split into two halves. GL5 is a small peotein, which is capable of fragment reconstitution spontaneously when split into two halves, GN and GC. Using GL5 as a model, different building blocks are designed to engineer self-assembling, physically crosslinked protein hydrogels. These novel hydrogels show temperature-dependent reversible sol-gel transition, and excellent property against erosion in water. It is anticipated that such fragment reconstitution may offer a general driving force for engineering protein hydrogels from a variety of proteins, expanding the horizon of “bottom-up” approaches in the design principles of biomaterials.

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Attribution-NonCommercial-NoDerivatives 4.0 International