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

The interactions between egg phosphatidylcholine monolayers and two su rface-active agents, sodium lauryl sulphate (SLS) and cetyltrimethylam monium bromide (CTAB), have been studied using a Langmuir-Blodgett fil m balance using a range of surfactant concentrations below the critica l micelle concentration. The presence of SLS in the subphase was shown to result in an increase in the surface pressure (using equivalent su rfactant solutions for comparison) while retaining the same basic shap e 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 interac t with the phospholipid monolayers by different mechanisms over the co ncentration ranges studied and that surface pressure measurements repr esent an effective means of characterising such interactions.