Barrett’s oesophagus (BE) is a non-malignant, specialised intestinal metaplasia of the oesophageal mucosa and a precursor of oesophageal adenocarcinoma (EAC). EAC is a particularly aggressive cancer with a high mortality rate, and as such, early intervention and prevention is considered to be imperative. In order to entertain such therapeutic strategies, the pathogenesis of BE needs to be better understood and models thereof developed to act as testing platforms for prophylactic candidates. BE pathogenesis is driven by persistent gastro-oesophageal reflux, which impairs mucosal barrier function, leading to epithelial ulceration, and initiates a sustained inflammatory response. This complex microenvironment reprogrammes both local cell types as well as the BE progenitor cell of origin (the identity of which remains under much debate). The pathogenic microenvironment presents selective pressures which act upon the reprogrammed cells, which express differing relative finesses – competitive exclusion of the local keratinocytes results in re-epithelialization of the wound site by the BE progenitor cell type. Early-stage pathogenesis, characterised by tissue function dysregulation and epithelial erosion prior to ulceration, is considered a potential point of prophylactic application. Moreover, the mucosa is a dynamic system and the evolution of tissue function in response to the periodic reflux insult is a complex, transient process. The objective of this work is thus to develop a platform capable of simulating the oesophageal mucosa and pathogenic microenvironment, while non-destructively monitoring the tissue function.

The oesophageal mucosa is a barrier tissue, responsible for modulating flux between lumen and stroma and as such, oesophageal tissue function is defined as its barrier function, or impedance to trans-epithelial flux. One means of probing barrier function is to measure the flux of solvated, ionic species across the epithelium, in response to an applied electrical potential difference. Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), a conjugated polymer blended with a poly-electrolyte, is identified as a suitable material upon which to base the platform, as it both allows for highly efficient ionic-to-electronic flux coupling as well as possessing mechanical properties similar to the extracellular material in native tissue. Using an ice-templating technique, the conjugated polymer can be fabricated so as to take the form of a macroporous scaffold, which can then be used as a cell-culture substrate, which enforces the three-dimensional architecture of native tissue. This scaffold was embedded within a suspended cell culture well-insert, with separate apical and basolateral compartments, to yield the electronic transmembrane (e-transmembrane) device. Colonising the scaffold with fibroblasts and culturing epithelium on the apical surface was shown to produce epithelial models which histologically recapitulated native tissue. Further, the device was shown to be capable of monitoring the linearized, ionic impedance of intestinal, endothelial and renal tubule epithelial models, with the correlation between measurement and barrier function confirmed through the use of epithelial tissue phantoms.

While the initial iteration of the e-transmembrane adheres to the conventional, two-electrode configuration, I have demonstrated a significant improvement in measurement sensitivity by extending the design to a three-electrode configuration, which incorporates a reference electrode. In particular, the utility of a non-conventional reference electrode design is demonstrated, wherein a polarizable material, shaped so as to minimize field and impedance distortion, is shown to improve sensor performance within the specific use context of the e-transmembrane device. The measurement error due to the reference electrode inclusion has been derived and verified by way of epithelial tissue phantoms, with the performance improvement illustrated in measurements of renal tubule epithelial models.

The e-transmembrane form-factor, which is an extension of conventional suspended cell-culture inserts, allows for the adaptation of existing three-dimensional tissue culture protocols; a commonly used oesophageal model, comprising of the co-culture of fibroblasts and immortalised oesophageal epithelial primary cells (EPC2-hTERT), is shown here to translate into the e-transmembrane, with the barrier function of the model measurable by the device. Periodic exposure to a simplified model of gastro-oesophageal refluxate simulates the early-stage pathogenic microenvironment in the e-transmembrane oesophageal model. I show that the model of early-stage pathogenesis displays erosion of the stratified epithelium and the activation of repair mechanisms in accommodation to the persistent insult. Ascorbic acid (vitamin C) is an anti-oxidant which has been shown to improve barrier function and wound healing in stratified squamous epithelia. I further demonstrate that concomitant exposure of the mucosal model to ascorbic acid and the refluxate results in reduced epithelial erosion and expedited barrier function repair, indicating the prophylactic utility of the dietary micronutrient.