A double injection ADSA-CSD methodology for lung surfactant inhibition and reversal studies

This paper presents a continuation of the development of a drop shape method for film studies, ADSA-CSD (Axisymmetric Drop Shape Analysis-Constrained Sessile Drop). ADSA-CSD has certain advantages over conventional methods. The development presented here allows complete exchange of the subphase of a spread or adsorbed film. This feature allows certain studies relevant to lung surfactant research that cannot be readily performed by other means. The key feature of the design is a second capillary into the bulk of the drop to facilitate addition or removal of a secondary liquid. The development will be illustrated through studies concerning lung surfactant inhibition. After forming a sessile drop of a basic lung surfactant preparation, the bulk phase can be removed and exchanged for one containing different inhibitors. Such studies mimic the leakage of plasma and blood proteins into the alveolar spaces altering the surface activity of lung surfactant in a phenomenon called surfactant inhibition. The resistance of the lung surfactant to specific inhibitors can be readily evaluated using the method. The new method is also useful for surfactant reversal studies, i.e. the ability to restore the normal surface activity of an inhibited lung surfactant film by using special additives. Results show a distinctive difference between the inhibition when an inhibitor is mixed with and when it is injected under a preformed surfactant film. None of the inhibitors studied (serum, albumin, fibrinogen, and cholesterol) were able to penetrate a preexisting film formed by the basic preparation (BLES and protasan), while all of them can alter the surface activity of such preparation when mixed with the preparation. Preliminary results show that reversal of serum inhibition can be easily achieved and evaluated using the modified methodology.