Biomaterial-Based Delivery of a Growth Factor and Cytokine Combination to Address Wound Healing Complications

Wound healing is a highly complex process that requires coordination of growth factors, cytokines, and cell types, in order to progress from an acute wound to a resolved scar. Healing complications, such as chronic wounds and scarring disorders, comprise a substantial health burden, and are linked to dysregulation of key growth factors and cytokines across multiple phases of healing. Standard care practices for these disorders are non-specific and often ineffective, and biologic treatments attempting to restore growth factor or cytokine balance to the wound have largely failed in the clinic, despite promising preclinical evidence. This thesis aimed to identify why delivery of growth factors and cytokines for wound healing complications has thus failed, and to evaluate strategies for improving their delivery using biomaterials. The first of two comprehensive literature review summarised the fact that the large-scale clinical failure of growth factor and cytokine delivery to wounds is likely due to the additive effects of poor and variable trial design and reporting, the incompatibility of topical administration, and issues relating to regulation and manufacturing. Biomaterials are an emerging novel strategy for tailored phasic and multiphasic release of proteins to wounds and have been proposed to address some issues identified with topical delivery. A second comprehensive literature review concluded that a multifaceted approach using multiple proteins within a composite biomaterial system may potentially be more therapeutically efficacious than previous topical delivery of single proteins in the clinic. However, there is still a lack of evidence that biomaterials actually provide proteolytic protection and structural support within the wound, and accurate comparisons to prove that they have improved efficacy compared to topical delivery of growth factors and cytokines. Limitations in this area of research are centered around translatability, with inconsistent model choices and non- human relevant outcome measures. Careful consideration needs to be applied when selecting which growth factors, cytokines and biomaterials to use, and these choices need to relate to targeting of multiple phases of wound healing and appropriate release kinetics. The second part of this thesis focused on development and testing of a biomaterial- based composite VEGF-E and vIL-10 delivery system to enable phasic regulation of wound inflammation, repair, and scarring. A biphasic release pattern was observed in vitro, with burst release of vIL-10 from the alginate hydrogel by day 1, and cumulative release of VEGF- E from lipid cubosome particles over 6 days. With only 52% release of VEGF-E and 2.3% release of vIL-10, more optimisation of protein loading is required. The lipid component of the system exhibited toxicity in human keratinocytes in vitro, but the hydrogel was well- tolerated when applied to murine skin wounds, with no significant adverse effects observed. ii Retention of hydrogels to the wound surface and cellular integration within the hydrogel were poor, so modifications are required to improve adherence and cell adhesion. Overall, this study highlighted many challenges in the development of growth factors and cytokines for the treatment of wound healing and scarring indications. A clear need was identified for streamlining of the preclinical and clinical pathways leading to approval. A more comprehensive and methodological approach to the development of growth factor and cytokine delivery systems that target the phasic dysregulation of chronic wounds or excessive scars was recommended as a strategy to facilitate the approval of much needed therapies for human wound indications