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Traditional methods for dermal wound closure such as sutures and staples are invasive and can result in soft tissue trauma, increasing the likelihood of localized inflammation and infections. Alternately, while tissue adhesive alternatives can effectively seal and adhere to the wounds, they can also present safety concerns relating to immunogenic responses and tissue toxicity. Herein, we fabricate injectable, adhesive, and cytocompatible poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA)-dopamine (DA) hydrogels co-crosslinked via hydrazone and self-polymerized dopamine crosslinks that exhibit high water retention, improved tissue adhesiveness, and effective tissue regeneration properties. POEGMA-DA hydrogels exhibit independently tunable gelation properties based on their dual crosslinking mechanism, allowing for gelation as fast as 24 s (allowing for injection and rapid filling of irregularly-shaped wounds) while achieving relevant compressive moduli of up to 37 kPa and in vitro skin adhesion strengths of up to 1.2 kPa. The POEGMA-DA hydrogels induced no significant inflammation while demonstrating high interfacial adhesiveness in a stented skin excisional mouse model, enabling efficient dermal tissue regeneration by supporting collagen remodelling and enabling the regeneration of hair follicles, sebaceous glands, and blood vessels at the excision site over the 14-day study timeline. As such, injectable POEGMA-DA hydrogels represent a relevant non-toxic and adhesive alternative wound closure system for treating deep dermal wounds. / Thesis / Master of Applied Science (MASc) / Effective wound healing and subsequent tissue regeneration after a physical injury requires a moist sterile environment, the presence of oxygen, nutrients and enzymes, an efficient blood supply to the wound site, and a controlled inflammatory response to initiate the healing process. External methods of closing the wound to prevent infection aid in faster healing like sutures, staples, and liquid sealants which can result in infections and/or the stimulation of an inflammatory response that can hinder tissue restoration. Hydrogels, water-swellable polymer networks, represent an alternative solution that can both suppress infection while simultaneously promoting wound healing. Hydrogels have a similar structure to soft tissues like skin and can thus provide a supportive environment for cells to promote tissue regeneration and restore tissue structure and function. The swelling of hydrogels in water is highly beneficial for providing moisture at the wound site; however, this high degree of water retention also means they have a hard time sticking to tissues. To address this challenge, hydrogels can be modified with a component naturally derived from marine mussels that allows them to stick to their wet habitats, helping hydrogels to stick to the wound site while healing. In this thesis, mussel-inspired hydrogels are designed and can spontaneously gel and stick to a wound site to accelerate the restoration of the structure and function of skin. These biodegradable and injectable hydrogels are effective in accelerating wound closure with minimal evidence of scarring while suppressing negative inflammatory reactions and restoring the structure of skin by promoting the regeneration of hair follicles, sebaceous glands and blood vessels.

Embryonic stem cells (ESCs) can differentiate into all somatic cells, and as such, are a promising cell source for therapeutic applications. In vitro, ESCs spontaneously differentiate via the aggregation of cells into embryoid bodies (EBs), which recapitulate aspects of early embryogenesis and harbor a unique reservoir of cues critical for tissue formation and morphogenesis. Embryonic healing responses employ similar intrinsic machinery used for tissue development, and these morphogenic cues may be captured within the EB microenvironment. Recent studies have shown that when injected into injury or defect models in vivo, ESCs synthesize and secrete extracellular factors that ultimately contribute to repair, suggesting that these molecules may be as important for regenerative therapies as functional differentiation of the cells. The overall objective of this project was to develop novel acellular matrices derived from differentiating ESCs undergoing morphogenesis. The central hypothesis was that embryonic matrices contain complex mixtures of extracellular factors that, when isolated, retain bioactivity and enhance wound healing in an adult environment. The overall objective was accomplished by: (1) investigating the production of extracellular matrix (ECM) by differentiating ESCs as a function of differentiation time; (2) assessing the ability of solvents to efficiently decellularize EBs; and (3) evaluating the healing response elicited by acellular matrices derived from EBs in a murine dermal wound healing model. Endogenous ECM synthesis by EBs varied with time and was associated with specific differentiation events. Novel techniques were developed to effectively remove cell components from EBs in order to extract complex, bioactive acellular matrices. EB-derived acellular matrices significantly enhanced the healing of excisional dermal wounds in mice, indicating the potency of extracellular factors synthesized by ESCs. All together, these studies demonstrate that acellular matrices derived from ESCs retain morphogenic factors capable of influencing tissue repair. In addition, this work lays the foundation for future studies to further examine the functional role of endogenous matrix molecules on ESC differentiation and to evaluate the utility of a stem cell-derived matrix for a variety of regenerative medicine applications.