This report presents a route map and the first steps to the development of a vascularised alveolarcapillary
barrier to study the effects of air pollution on lung-health and chronic respiratory diseases.
The ultimate goal is to fabricate a vascularised model of an alveolar-capillary barrier, that
mimics the physiology of the human lung more closely than currently used models. Current vascularised
alveolar-capillary barrier models are limited by the absence of membrane-free designs
and the lack of integration of both fluid flow and membrane stretching. The development of a
membrane-free, vascularised model that integrates fluid flow and membrane stretching, requires a
reproducible vascularisation method with a lifespan sufficient for epithelial cell differentiation and
follow-up experiments. Pre-structured vessels provide more control of the structure of the vessel
network and improve the reproducibility of a model compared to a model with a self-assembled
vascular network. Therefore, the first step in this study is to establish a method for culturing a
lung-derived endothelial vessel in a pre-formed channel within hydrogel as extracellular matrix
that can last several weeks. Wire moulding is used to create a hollow channel inside a fibrinogenbased
hydrogel between two injection needles. Two diameters of wires, 50 μm and 125 μm, and
two concentrations, 1% and 2%, of fibrinogen were used for a total of 10 tests. The endothelial
cells were seeded using the capillary effect and after four hours, the perfusion of medium through
the channels started. A pre-formed channel in the hydrogel containing 2% hydrogel and seeded
with lung-derived endothelial cells remained perfusable for 32 days while withstanding flow leading
to a significant amount of shear stress on the endothelial cells. To study the phenomena of
gas exchange that accur across larger tissue constructs, the hierarchical dimensions and topological
complexity of native vascular beds should be better replicated. Another moulding method
is needed to create a structure of hollow channels inside a hydrogel to culture a vascular network
rather than one vessel. It was found that with carbohydrate glass, varying structures can be
printed and it can be embedded within hydrogel prior to cross-linking without blending into
one another. This indicates that sacrificial moulding using carbohydrate glass is a promising
technique for creating pre-structured vascularised networks. This potential method to create a
pre-structured network combined with our cell seeding method and the 2% fibrinogen hydrogel,
is the basis for the development of a reproducible, membrane-free vascularised alveolar-capillary
barrier model that incorporates flow and stretching of the barrier.