A microfluidic-based bubble generation platform enables analysis of physical property change in phospholipid surfactant layers by interfacial ozone reaction.

The air-liquid interface filled with pulmonary surfactant is a unique feature of our lung alveoli. The mechanical properties of this interface play an important role in breathing and its malfunction induced by an environmental hazard, such as ozone, relates to various lung diseases. In order to understand the interfacial physics of the pulmonary surfactant system, we employed a microfluidic bubble generation platform with a model pulmonary surfactant composed of two major phospholipids: DPPC (1,2-dipalmitoyl-sn-phosphatidylcholine) and POPG (1-palmitoyl-2-oleoyl-sn-phosphatidylglycerol). With fluorescence imaging, we observed the ozone-induced chemical modification of the unsaturated lipid component of the lipid mixture, POPG. This chemical change due to the oxidative stress was further utilized to study the physical characteristics of the interface through the bubble formation process. The physical property change was evaluated through the oscillatory behaviour of the monolayer, as well as the bubble size and formation time. The results presented demonstrate the potential of this platform to study interfacial physics of lung surfactant system under various environmental challenges, both qualitatively and quantitatively.