Tunable microstructured membranes in organs-on-chips to monitor transendothelial hydraulic resistance

Tissue engineering is an interdisciplinary field, wherein scientists from different backgrounds collaborate to address the challenge of replacing damaged tissues and organs through the in vitro fabrication of functional and transplantable biological structures. Because the development and optimization of tissue engineering strategies rely on the complex interaction of cells, materials, and the physical-chemical tissue microenvironment, there is a need for experimental models that allow controlled studies of these aspects. Organs-on-chips (OOCs) have recently emerged as in vitro models that capture the complexity of human tissues in a controlled manner, while including functional readouts related to human organ physiology. OOCs consist of multiple microfluidic cell culture compartments, which are interfaced by porous membranes or hydrogels in which human cells can be cultured, thereby providing a controlled culture environment that resembles the microenvironment of a certain organ, including mechanical, biochemical, and geometrical aspects. Because OOCs provide both a well-controlled microenvironment and functional readouts, they provide a unique opportunity to incorporate, evaluate, and optimize materials for tissue engineering. In this study, we introduce a polymeric blend membrane with a three-dimensional double-porous morphology prepared from a poly(ϵ-caprolactone)-chitosan blends (PCL-CHT) by a modified liquid-induced phase inversion technique. The membranes have different physicochemical, microstructural, and morphological properties depending on different PCL-CHT ratios. Big surface pores (macrovoids) provide a suitable microenvironment for the incorporation of cells or growth factors, whereas an interconnected small porous (macroporous) network allows transfer of essential nutrients, diffusion of oxygen, and removal of waste. Human umbilical vein endothelial cells were seeded on the blend membranes embedded inside an OOC device. The cellular hydraulic resistance was evaluated by perfusing culture medium at a realistic transendothelial pressure of 20 cmH₂O or 2 kPa at 37°C after 1 and 3 days postseeding. By introducing and increasing CHT weight percentage, the resistance of the cellular barrier after 3 days was significantly improved. The high tuneability over the membrane physicochemical and architectural characteristics might potentially allow studies of cell-matrix interaction, cell transportation, and barrier function for optimization of vascular scaffolds using OOCs.