Molecular organization of antibiotic amphotericin B in dipalmitoylphosphatidylcholine monolayers induced by K(+) and Na(+) ions: the Langmuir technique study.

The effect of potassium (K(+)) and sodium (Na(+)) ions on the self-association of antibiotic amphotericin B (AmB) in the lipid membrane was reported. Mixed Langmuir monolayers of AmB and dipalmitoylphosphatidylcholine (DPPC) were investigated by recording surface pressure-area isotherms spread on aqueous buffers containing physiological concentration of K(+) and Na(+) ions. The analyses of the π-A isotherms and compressional modulus curves indicate the interactions in the AmB-DPPC system. The strength of the AmB-DPPC interactions and the stability of the mixed monolayers were examined on the basis of the excess free energy of mixing values. The obtained results proved a high affinity of AmB towards lipids induced by the presence of K(+) than Na(+) ions. The most stable monolayers in the presence of K(+) and Na(+) ions were formed by AmB and DPPC with the 1:1 and 2:1 stoichiometry. The understanding of the AmB aggregation processes at the molecular level should contribute to elucidate the mechanisms of action and toxicity of this widely used drug. The presented results are potentially valuable in respect to develop more efficient and less toxic AmB formulations.