The alveolus-on-a-chip: a biomimetic, microfluidic in vitro model of the alveolar-capillary barrier

The lung disease burden has increased due to some factors such as pollution, smoking, pathogenic bacteria and virus. Among them, lung cancer has become the leading cause of cancer death worldwide due to its high recurrence, metastasis formation and drug resistance. For these reasons, in vitro models that reproduce the lung environment and individualized treatment are required to improve therapies efficacy. Organs-on-chips can be a powerful technology to accomplish this goal. In this thesis work, an alveolus-on-chip, which mimics the alveolar-capillary barrier, is described. The developed microfluidic device consists of two layers separated by an electrospun polycaprolactone/gelatin (PCL/Gel) membrane, where the co-culture of lung epithelial cells (A549) and lung endothelial cells (Hulec-5a) was performed by seeding the two cell lines in the upper and bottom layer of the PCL/Gel membrane, respectively. In addition, the chip allows for carrying out the breathing motion by the mechanical stimulation of the membrane and to generate the air-liquid interface (ALI) on the co-culture for reproducing an in vivo-like ambient. The device was designed through Rhinoceros and fabricated using the replica molding technique by casting polydimethylsiloxane (PDMS) inside the mold (obtained by laser ablation of polymethylmethacrylate (PMMA)). The achieved devices were analysed by optical microscopy showing that the geometry was reproduced correctly maintaining the desired dimensions. Instead, the electrospinning technology was exploited to fabricate PCL and PCL/Gel membranes, whose morphology was analysed through scanning electron microscopy while uniaxial and biaxial cyclic tests were used to measure their mechanical properties. All the membranes revealed a random configuration and good fatigue resistance, in particular PCL/Gel nanofibers showed to be bead-free and with small diameters. Finally, the cellular adhesion on the two sides of the polymeric substrates was analysed through the staining of the nuclei and the actin filaments of A549 and Hulec-5a with DAPI and phalloidin, respectively. Results suggest that cells adhere better on PCL/Gel membrane, as demonstrated in cell viability assay (resazurin) which was conducted to monitor cells metabolic activity inside the device. This thesis work was carried out under the DEFLECT (“Advanced platform for the early detection of not small cells lung cancer”) project, financed by Piedmont Region in the framework of “Health & WellBeing” Platform.