AN INVESTIGATION INTO THE EFFECTS OF SURFACTANTS ON PHOSPHOLIPID MONOLAYERS USING A LANGMUIR-BLODGETT-FILM BALANCE

The interactions between egg phosphatidylcholine monolayers and two surface-active agents, sodium lauryl sulphate (SLS) and cetyltrimethylammonium bromide (CTAB), have been studied using a Langmuir-Blodgett film balance using a range of surfactant concentrations below the critical micelle concentration. The presence of SLS in the subphase was shown to result in an increase in the surface pressure (using equivalent surfactant solutions for comparison) while retaining the same basic shape and transitional behaviour of the phospholipid profile. In contrast, the presence of CTAB resulted in a concentration dependent inhibition of film formation. It is concluded that these two surfactants interact with the phospholipid monolayers by different mechanisms over the concentration ranges studied and that surface pressure measurements represent an effective means of characterising such interactions.