Submitted on May 14, 2008
Revised on June 27, 2008
Accepted on July 18, 2008
High throughput evaluation of pulmonary surfactant adsorption and surface film formation
Andrea Ravasio, Antonio Cruz, Jesus Pérez-Gil, and Thomas Haller
Department of Physiology and Medical Physics (Division of Physiology), Innsbruck Medical University (MUI), Innsbruck, Tirol A-6020
Corresponding Author: andrea.ravasio{at}i-med.ac.at
The assessment of new therapeutic strategies to cure surfactant associated lung disorders would greatly benefit from assay systems allowing routine evaluations of surfactant functions. We present a method to measure surfactant adsorption kinetics into interfacial air-liquid interfaces based on fluorescence microplate readers. The principle of measurement is simple, robust and reproducible: Wells of a microtiter plate contain an aqueous solution of a light absorbing agent. Fluorescence is excited and collected from the top of the wells so that fluorescently labeled surfactant injected into the bulk can be detected only once adsorbed into the air-liquid interface. Mass transfer from the bulk to the interface is achieved by orbital shaking implemented in the plate reader instrument. The method has been tested and validated by using phospholipids or surfactants of different origins, by using albumin as surfactant inhibitor, and by comparison of results with Wilhelmy balance measurements. The method is suited to be implemented in high throughput screening routines for conditions affecting, or improving, surfactant film formation. In contrast to surface tension measurements, our method gives a direct read out of the amount of surfactant adsorbing into the interface, including the functionally important amount of material firmly associating with the interfacial film.
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