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Biophys. J. BioFAST: First Published June 10, 2005. doi:10.1529/biophysj.104.053132
© 2005 by the Biophysical Society.

A more recent version of this article appeared on August 1, 2005.
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SPECTROSCOPY, IMAGING, OTHER TECHNIQUES

Optical measurement of surface tension in a miniaturized air-liquid interface and its application in lung physiology

Cristina Bertocchi 1, Andrea Ravasio 1, Stefan Bernet 1, Guenther Putz 1, Paul Dietl 2 and Thomas Haller 1*

1 Medical University Innsbruck
2 University of Ulm

* To whom correspondence should be addressed. E-mail: thomas.haller{at}uibk.ac.at.

Submitted on September 16, 2004
Revised on October 13, 2004
Accepted on 26 May 2005


  Abstract
We have previously shown that lamellar body-like particles (LBPs), the form in which pulmonary surfactant is secreted, spontaneously disintegrate when they contact an air-liquid interface, eventually creating an interfacial film. Here, we combined these studies with a new technique enabling the simultaneous and non-invasive measurement of surface tension ({gamma}). This method is a refinement of the pendant drop principle. A sapphire cone with a 300 µm aperture keeps the experimental fluid by virtue of surface coherence in a fixed and nearly planar position above the objective of an inverted microscope. The radius of curvature of the fluid meniscus is related to {gamma} and determines the pattern of light back-reflection upon epiillumination. This method, which we name 'inverted interface', has several novel aspects, in particular its microscopic dimensions. When using LBPs freshly released by alveolar type II cells, we found that their conversion at the interface resulted in {gamma}-reduction close to 30 mN/m. After a fast initial decay, {gamma}-decrease proceeded slowly and in proportion to single particle conversions. These conversions ceased with time whereas {gamma} decreased further, probably due to reorganization of the already deposited material. The present investigation indicates that surface film formation by adsorption of large surfactant aggregates is an important mechanism by which {gamma} is reduced in the lung.

Key Words: adsorption, alveolus, lamellar body, pulmonary surfactant, spreading




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A. Ravasio, A. Cruz, J. Perez-Gil, and T. Haller
High-throughput evaluation of pulmonary surfactant adsorption and surface film formation
J. Lipid Res., November 1, 2008; 49(11): 2479 - 2488.
[Abstract] [Full Text] [PDF]


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Copyright © 2005 by the Biophysical Society.