Nanostructure of the aqueous form of lung surfactant of different species visualized by cryo‐transmission electron microscopy

Cryogenic temperature transmission electron microscopy (cryo-TEM) makes it possible to study the nanostructure of a wide range of fluid phases with a high degree of preservation. Most studies based on scanning electron microscopy or TEM employ specimen preparation techniques that give extraordinary results for tissues, but alter the native structure of complex fluid substances such as lung surfactant. In this paper, we evaluated direct-imaging cryo-TEM as a method to study the morphology of the aqueous form of lung surfactant. We compared the morphology of samples obtained from different species, and cryo-TEM data to data obtained by staining-and-drying. We demonstrate that cryo-TEM preserves and images much better sample morphology and fine details of the surfactant structures. We show that cryo-TEM, a method based on physical fixation, which avoids chemical changes and aggregate rearrangement, is a most useful tool to further our understanding of lung surfactant and its function.