Molecular characterization of lung surfactant could lead to better treatment of respiratory diseases

A team of researchers led by engineering researchers at the University of Minnesota-Twin Cities analyzed the basic properties and structure of lung surfactants

The paper was published in Science Advances, a peer-reviewed, multidisciplinary scientific journal published by the American Association for the Advancement of Science

The lungs of both humans and animals naturally produce a surfactant, a substance composed of lipids and proteins that coats the lungs and lowers surface tension when we inhale and exhale, making breathing easier

Respiratory diseases such as pneumonia or COVID-19 can hinder the proper working of lung surfactants, leading to respiratory complications

"The primary purpose of pulmonary surfactant is to reduce the energy required to breathe," said lead author Cain Valtierrez-Gaytan, a doctoral student in the Department of Chemical Engineering and Materials Science at the University of Minnesota.

While lung surfactants are composed of many different materials, the University of Minnesota team was initially interested in the role of cholesterol, a lipid that occurs naturally in animal and human cells

Using Langmuir troughs as well as high-resolution optical microscopy, images were studied of some of the lipid constituents of the lung surface—dipalmitoylphosphatidylcholine, cetyl alcohol, palmitic acid, and dihydrocholesterol—at the monolayer level, or films composed of a layer of molecules in air and interface between water

First, the researchers found that surfactants organize in an equilibrium structure, meaning that if the crystalline parts of the molecule change shape and grow as pressure increases, they have the ability to return to their original shape if the pressure is removed

The microscope images also showed that when the pressure was increased, the crystalline parts of the monolayer became "fingers," or elongated

"We can use fundamental materials science theories, such as instability and equilibrium, to try to understand how lung surfactants work," said senior author Joe Zasadzinski, a professor in the University of Minnesota's School of Chemical Engineering and Materials Science