Impact of membrane-lipid additives on the structure and morphology of nanoerythrosomes.

The synthetic forms of natural lipid components are advantageous additives in the size and shape tailoring of erythrosomes for making them more apt for various purposes, including medical drug carrying and biosensors. The cell membranes of emptied erythrocytes, known as ghosts, undergo structural and morphological rearrangement on the uptake of additional amounts of their characteristic lipids. The different morphologies, observed by freeze-fractured transmission electron microscopy, are associated with the changes of lipid-lipid and lipid-protein interactions on the atomic scale, as shown by infrared spectroscopy. The shape of the occurring nanoparticles is strongly dependent on the types of added lipids. Lipids from the inner leaflet (phosphatidylethanolamines and -serines) induce flat layer fragments - which can not consider as erythrosomes -, while those characteristic for the outer leaflet (phosphatidylcholines and sphingomyelins) cause the formation of vesicle-like spherical nanoerythrosomes and alter the conformation of ghost-membrane proteins, witnessed by the increase of the helix to sheet ratio by 30%. Addition of all four characteristic membrane lipids induces less regularly shaped nanoerythrosomes, indicating the effects of both lipid groups. Despite the different shapes of the occurring objects, their sizes are in a similar domain, thus further 3D information, readily provided by freeze-fractured transmission electron microscopy, is necessary to distinguish the shape and type of these nanoparticles.