Identifying distinct oxygen diffusivity through type I pneumocyte-like cell layers using microfluidic device

Oxygen is necessary for cellular respiration in aerobic organisms. In animals, such as human, inhaled oxygen moves from the alveoli to the blood through alveolar epithelium into pulmonary capillaries. Up to now, different studies have been reported to examine experimental oxygen diffusivity for simple membrane or single-celled organisms; however, devices capable of precisely characterizing oxygen transportation through cell layers with dimensions similar to their physiological ones have not been developed. In this study, we establish an integrated approach exploiting a multi-layer microfluidic device and relative fluorescence lifetime detection apparatus to reliably measure oxygen diffusivity through a cell layer. In the experiments, different types of cells, including A549 and 3T3 cell lines, lung stem/progenitor cells, and the differentiated type I pneumocyte-like cells, are used to form cell layers within the devices for their oxygen diffusivity evaluation. A distinct facilitated oxygen transportation behavior of the differentiated type I pneumocyte-like cells that has never been discussed before is identified using the approach. The study offered a new in vitro approach to evaluate the oxygen diffusivity across cell layers in a microfluidic device and open a door to construct more physiologically meaningful in vitro model system to study respiratory systems.