Development of a dual flow microfluidic device for the study of barrier systems

Inflammatory Bowel Diseases (IBD) including Crohn's Disease and Ulcerative Colitis are chronic conditions characterised by inflammation of the wall of the gastrointestinal tract. IBD has also been shown to have systemic impacts including on the central nervous system. Traditional models including the animal systems provide only limited information due to a lack of clinical relevance. Microfluidic technology offers a solution, allowing for the creation of human models which better consider the biophysical properties seen within an organ. This study aimed to develop and optimise a dual flow microfluidic device for the study of the gut and blood-brain-barrier (BBB) systems. Devices were designed in-house and consisted of two channels separated by a semi-permeable membrane. A series of iterations of the device were examined for gut-chip studies, with the device refined and optimised to allow a culture of colonic epithelial cells to be maintained for 7 days. Permeability studies and visualisation of ZO-1 expression showed the maintenance of barrier properties during this time. Following optimisation of the gut-chip, the inflammatory effects of bacterial products on epithelial cells were examined. Treatment with bacterial products induced an inflammatory response in the model, however this was lowered in comparison with a static model. Adaption of the device to culture endothelial cells and astrocyte cells in a BBB model was also carried out. Viability tests showed the device could maintain a variety of cell lines for at least 96 h on chip. The gut and BBB-chip were then connected in series, creating a dual model. This platform could maintain a co-culture of epithelial cells within the gut-chip and endothelial cells within a BBB-chip for at least 48 h, showing the potential of the dual flow device to allow for more systemic studies. Preliminary studies were undertaken using a modification of the gut-chip for the maintenance of full thickness gut tissue biopsies for up to 72 h on chip, however morphology of the tissue was not well-preserved. In summary, this study examined the development and optimisation of a dual flow microfluidic device for the study of barrier systems. The final iterations of the device were both robust and reliable and are suitable for investigating a wide variety of physiological and pathological barriers and potentially provide an alternative to existing animal and cellular models.