Development of Printable Lung-on-a-chip by using Mountable Cell Culture Insert

Through an inkjet bio-printing, we have previously developed a novel 3D-structured lung model. Despite the advantages of its structural property and functions, it is necessary to combine the model with lung-on-a-chip to mimic the blood flow at the epithelial-blood barrier interface. However, printing inside the chip was a challenging issue because it is difficult to print a bioink directly into the inner chip module. Thus, we constructed an open-structured chip in a form that can be integrated with a mountable cell culture insert that is known as suitable for inkjet printing. The chip consists of lower and upper PDMS layers for microfluid circulation and the cell culture insert, respectively. This chip utilizes the elasticity of PDMS to hold the cell culture insert firmly to prevent leakage during media supplying. It also contains a pressure regulating system to prevent a high internal pressure which may cause the penetration of the membrane in cell culture insert by media overflow. The cultured tissue on a cell culture insert after the layer-by-layer inkjet printing was mounted to the upper layer, and media was infused into the microchannel of the lower layer to induce the model to be cultured under flowing conditions. To verify this system, a 3D-structured lung model fabricated by inkjet printing was mounted on the chip. After cultured for 7 days, the tissue was evaluated with TEER measurement and identified with H&E staining. The TEER values show that the lung model cultured through this system has robust tight junctions similar to that cultured under non-flow conditions. Through the H&E staining, the histological structure of the tissue was also confirmed that the printed lung tissue was not damaged during the process of being cultured in the chip. Furthermore, by comparing lung models under various flow rate conditions with tissues cultured in conventional well plates, the effect of shear stress on inkjet-printed lung models was analyzed. Considering that this system can be easily integrated with various tissues fabricated by inkjet printing, we expect that it may contribute to a reliable measurement and analysis tools in organ-on-a-chip researches.1