Studying the interfacial activity and structure of pulmonary surfactant complexes

• Published in: Chemistry and physics of lipids 2025-01, Vol.266, p.105459, Article 105459
• Main Authors: Collada, Ainhoa, Cruz, Antonio, Pérez-Gil, Jesús
• Format: Article
• Language: English
• Subjects: Air-liquid interface; Atomic force microscopy; Langmuir surface balance; Pulmonary surfactant; Scattering; Surfactometer
• ISSN: 0009-3084; 1873-2941; 1873-2941
• DOI: 10.1016/j.chemphyslip.2024.105459

Pulmonary surfactant (PS) is a membranous complex that coats the respiratory air-liquid interface in air-breathing animal lungs. Its main function is to minimize the surface tension at the end of expiration, what is needed for preventing alveolar collapse. Although the tension reduction capabilities of surfactant depend on the formation of air-exposed phospholipid-enriched monolayers, the interfacial surfactant films are far from simple monolayers. Surfactant surface films are dynamically interconnected to continuously secreted newly synthetized material thanks to the action of a pair of very hydrophobic proteins, termed SP-B and SP-C, which are responsible to modulate the biophysical behavior of the complex. Other proteins in the system, such as the hydrophilic SP-A and SP-D, are integrated into different surfactant structures but participate primarily in the immune defense of the lung. In spite of countless studies on the structure and chemico-physical properties of surfactant membranes, the full complexity of surfactant three-dimensional structure is far from being completely understood. Here we review some of the most useful techniques that have allowed the characterization of the PS system along the years to develop the current models interpreting surfactant structure-function relationships. •The main techniques used for studying the interfacial activity of PS have been historically reviewed.•The role of 3D structure for the biophysical function of PS membranes and films is emphasized.•Surface balances and the most relevant surfactometers are described and how they help to understand PS dynamics.•New techniques have been developed for the study of PS three-dimensional structures.