Foam appears when α1 protease inhibitor (α1 PI) is solubilised and nebulised. The purpose of this study was to select antifoams likely to be associated with an α1 PI to be nebulised and to reveal the interactions between α1 PI and the antifoams tested. Antifoam efficacity as regards α1 PI solution, was evaluated by measuring antifoaming capacity and examining foam stability. The surface tensions of the antifoam solutions and of the α1 PI solution alone or with antifoams were determined. The influence of the antifoam concentration was evaluated. The compounds tested show high antifoam capacity. Our study revealed different types of foam destabilisation processes: firstly through interactions with α1 PI in solution, modifying protein diffusion properties at the interface; secondly through a competitive phenomenon at the interface which leads to a total displacement of the protein or to a mixed him containing both protein and surfactant. Span 65 at a 0.025% concentration and cetyl alcohol at a 0.05% concentration associated with tyloxapol at a 0.025% concentration have an antifoaming capacity compatible with the pulmonary administration of α1 PI. For these compounds, the surface tension study of the different solutions made it possible to reveal the formation of a mixed film containing both protein and antifoam at the interface.
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