Confocal Laser Scanning Microscopy and Model Membranes to Study Translocation Mechanisms of Membrane Active Peptides

Membrane active peptides hold great potential for targeted drug delivery systems and understanding their mechanism of uptake is a key step in the development of peptide based therapeutics and clinical use. Giant unilamellar vesicles are cell-sized model membranes that can be individually observed under the microscope. The lipid composition of these membranes can be controlled, and interaction with peptides and changes induced by the peptides can be directly followed. Relevant information on the specific steps of peptides uptake can be obtained using membranes of different lipid composition. The present work provides a selection of dynamics and kinetics of peptides at interaction with model membranes of different lipid composition. The systematic peptide-membrane interaction was investigated by laser scanning confocal microscopy. The peptides used in this study neither internalized nor induced pore formation in neutral membranes composed of phosphatidylcholine and cholesterol. In membranes with anionic phosphatidylserine or cone-shaped phosphatidylethanolamine, all peptides internalized but only two of them were able to form pores, showing that the length of the peptide, the numbers of the arginine amino acid or the length of the α-helix are also relevant for the penetration efficiency of peptides.