Gilmartin, DJ; (2015) The design of a synthetic, bioactive dermal scaffold to assist the healing of chronic, non-healing wounds. Doctoral thesis , UCL (University College London).

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Abstract

Chronic ulcers are painful, hard-to-heal wounds. To assist the healing of full-thickness ulcers and burns, engineers have designed scaffolds; synthetic skin substitutes intended to act as a temporary structure to support cell growth and wound regeneration. Remarkably few studies have investigated the effect of scaffolds on healing at the cellular level, however. Owing to the lack of clear evidence, the initial project aim was to investigate the function of scaffolds in vivo, with the hypothesis "scaffolds do not promote healing of full-thickness wounds." After applying fabricated collagen scaffolds to full-thickness wounds, scaffolds appeared to integrate with the wound edge poorly. Wound edge keratinocytes were found to express markedly elevated levels of the gap junction proteins connexin 43 (Cx43) and Cx26, surprisingly similar to chronic wounds. In an effort to improve integration, scaffolds were bioactivated through local application of a Cx43 antisense sequence (asODN). This significantly reduced wound edge Cx43 expression, epithelial thickening and inflammation of the surrounding tissue compared to using ordinary scaffolds, yet healing still occurred underneath scaffolds without matrix integration. An alternative hypothesis was formulated; that "scaffolds could instead be used to deliver drugs to render them beneficial in ulcer treatment." To achieve this, scaffolds were polymer coated with Cx43 asODN using an emulsion technique, and asODN elution was confirmed in vitro to occur over several days using UV spectrophotometry. Application of coated Cx43 asODN scaffolds significantly improved wound re-epithelialisation, even over untreated wounds, and prevented scaffold-associated adverse effects. Incorporation of novel Cx26 antisense sequences also significantly reduced wound edge Cx26 levels and improved re-epithelialisation. Wounds treated with combined Cx26 and Cx43 asODN scaffolds typically re-epithelialised further still, such that using both sequences may be synergistic. These findings support the use of coated scaffolds as drug delivery mechanisms that could be developed to treat chronic wounds.

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