A SPREADING TECHNIQUE FOR FORMING FILM IN A CAPTIVE BUBBLE

Mechanisms underlying the surface properties of lung surfactant are ex tensively studied in in vitro systems such as the captive-bubble surfa ctometer (CBS), the pulsating-bubble surfactometer, and the Wilhelmy b alance. Among these systems, the CBS is advantageous when a leakproof system and high cycling rates are required, However, widespread applic ation of the CBS to mechanistic studies of dynamic surfactant protein- phospholipid interactions of spread film and to comparative studies be tween spread and adsorbed film is hampered because spreading of film i s difficult. In addition, when film is formed by adsorption, the amoun t of material required is fairly large. We have developed an easy spre ading technique that allows routine formation of film by spreading of small amounts of surfactant components at the air-water interface of a n air bubble in a CBS, The technique is reliable, precise, and accurat e, and the biophysical activity of film formed by spreading is similar to that of film formed by adsorption. This method will be useful for mechanistic studies of surfactant components under dynamic conditions and for comparative studies of spread films and adsorbed films.