The influence of phospholipid structure on the interactions with nystatin, a polyene antifungal antibiotic A Langmuir monolayer study

This work presents the investigations of the interactions between nystatin, a polyene antibiotic, and phospholipids with various head groups (phosphatidylcholine and phosphatidylethanolamine) and acyl chains of different length and saturation degree. The experiments were performed with the Langmuir monolayer technique. Among phosphatidylethanolamines, DMPE, DPPE and DSPE were studied, while phosphatidylcholines were represented by DSPC and DOPC. The influence of the antibiotic on the molecular organization of the phospholipid monolayer was analysed with the compression modulus values, while the strength of nystatin/phospholipid interactions and the stability of the mixed monolayers were examined on the basis of the excess free energy of mixing values. The results obtained proved a high affinity of nystatin towards phospholipids. Nystatin was found to interact more strongly with phosphatidylcholines than with phosphatidylethanolamines. The most negative values of the excess free energy of mixing observed for the antibiotic and DOPC mixtures prove that nystatin favors the phospholipid with two unsaturated acyl chains. The results imply that nystatin/phospholipid interactions compete in the natural membrane with nystatin/sterol interactions, thereby affecting the antifungal activity of nystatin and its toxicity towards mammalian cells.