Functional and Structural Characterization of a Lyophilized Pulmonary Surfactant Directly Applied onto the Air-Liquid Interface

Abstract

Lung surfactant is a lipoproteic complex which main function is to stabilize the air-liquid interface in the alveolous. Its absence or inactivation leads to severe lung damage which can cause death. Up to now, clinical treatments have consisted in the intratraqueal application of a dense aqueous suspension, an invasive procedure that requires intubation of the patient. In an attempt to explore new ways of administration such as powder aerosolization, we have evaluated the functional behavior and structural features of the films formed by lyophilized membranes of porcine lung surfactant directly applied onto the air-liquid interface. Captive Bubble Surfactometry experiments have demonstrated that lyophilization preserves the main characteristics of a functional surfactant such as a fast adsorption and a rapid extension along the interface. Even more, it was demonstrated that less amount of material is needed to obtain the same results compared to an aqueous suspension. This more active material exerts also a higher resistance to the inactivation of the surfactant function that is produced by serum components. The effect of the freezing temperature previous to the sublimation process was also evaluated to stablish the proper conditions needed to observe such results. Surfactant films formed from the direct application of lyophilized fluorescent labeled surfactant complexes at the interface of a Langmuir balance, provided some light upon the possible mechanism that underlies this behavior.