Stability of foam lipid bilayers of amniotic fluid

Abstract

Black foam lipid films are studied, having been obtained by thinning of foam films stabilized with phospholipids of amniotic fluid (AF). Whilst in a suitable measuring cell, the black films are in contact with air (normally) and with a solution of AF (laterally). It is proved experimentally that the black films studied are bilayer ones. The probability W for observation of black foam film in a critically thick foam film is described on the basis of the theory of rupture of bilayers due to nucleation of holes in them. This probability can characterize the stability of the bilayer foam film, as it depends strongly on the concentration C of phospholipids in the AF solution. The experimentally determined W exhibits a steep dependence on C and shows the existence of a threshold concentration below which a black foam film is not observed. A correlation is established between the threshold concentration of phosphatidylcholines (PC) and that PC concentration which ensures functionally the human foetal lung maturity. On this basis is developed a diagnostic method for assessing the foetal lung maturity which is characterized by high reliability, rapidity and use of a small quantity of AF. It is proved that PC is the lipid which builds up the foam bilayer obtained from AF and it is found that a PC concentration of 46 μg cm −3 in the AF ensures foetal lung maturity.