Poly(trimethylene carbonate)-based membranes for biomimetic lung epithelial-endothelial models

Lung diseases are one of the most common causes of death. Moreover, the rise of lung-associated viruses, such as SARS-CoV-2, emphasise the relevance of and need for lung models that generate reliable data of potential drugs and treatments. Thus, lungs-on-chips (LOCs) have been developed, which implement more physiological features, e.g. microfluidics and mechanical stretch of cells, than traditional lung models to better mimic the tissue, and thus yield more reliable results. However, the properties of the porous membranes on which the cells in LOCs and lung models in general are cultured, are often overlooked, while these properties are known to influence cell behaviour. For example, many membranes are made from stiff materials, which do not reflect the stiffness of the lungs and do not allow mechanical stretch. In this thesis, we used poly(trimethylene carbonate) (PTMC), a cytocompatible, flexible material. We developed porous and form-stable PTMC membranes using temperature-induced, liquid-induced and evaporation-induced phase separation (i.e. TIPS, LIPS and EIPS, respectively) together with photo-crosslinking. Different parameters were changed to influence membrane properties. For TIPS, we focused on lowering the temperature during crosslinking. With LIPS, we looked at the effects of pore formers and crosslinking on membrane properties. Using EIPS, we investigated e.g. the effects of the molecular weight of PTMC, the non-solvent type and concentration, and the temperature and humidity during EIPS. We also combined EIPS with micromoulding to produce membranes with alveoli-like microwells. The different membranes were characterised, including their morphology, gel content and water permeance. We developed a lung epithelial-endothelial model of Calu-3 lung epithelial cells and human lung microvascular endothelial cells (LMVECs) on the flat and microstructured EIPS-based membranes. The models were characterised through Zona Occludens-1 (ZO-1)/CD31 and live/dead staining, as well as electrical resistance and FITC-dextran permeability assays. Stainings for epithelial- and endothelial-to-mesenchymal transitions (EMT and EndoMT, respectively) were also performed. Lastly, the co-culture model on the microstructured membranes was integrated in a commercial organ-on-chip platform and ZO-1/CD31 and live/dead staining were performed on this model. The presented novel fabrication methods and PTMC membranes could lead to the use and development of more biomimetic membranes and LOCs.