Study of the interaction of beta-cyclodextrin with phospholipid monolayers by surface pressure measurements and fluorescence microscopy

The interaction of beta-cyclodextrin (beta-CD) with different lipids has been studied, using Langmuir monolayers kept at constant surface pressure or constant spreading surface. Results show that beta-CD, injected beneath the monolayer, is able to desorb unsaturated palmitoyloleoylphosphatidylcholine (POPC) and sphingomyelin (SM) under specific experimental conditions. In this last case, SM monolayers, labeled with the fluorescent NBD-PC probe, were also observed by fluorescence microscopy, before and after beta-CD injection. Images show that SM monolayers are more homogeneous after beta-CD injection, because of the lipid desorption. At last, it seems that lipid desorption occurs only in a restricted surface pressure range, depending on the lipid.