Alterationsin Membrane Lipids of Live Red Blood Cellsaffecttheir Interactions with Exogenous Particles

Abstract

The mammalian cell membrane is a lipid bilayer, which is asymmetric with respect to its phospholipid composition. Cyclodextrins, a group of cyclic molecules with a highly hydrophobic cavity and hydrophilic exterior, have been shown to mediate the exchange of exogenous phospholipids with bilayer membranes. We previously implemented this method to report the type and species of phospholipids in the outer leaflet of red blood cells (RBCs). In this study, we use phospholipid exchange to elucidate the role of phospholipids in nanoparticle interactions with RBC membranes. We exchanged the outer leaflet of RBCs with phospholipids of interest, using methyl-α-cyclodextrin and studied nanoparticles interaction with the membrane. Multiple phospholipids, including sphingomyelins (SM), phosphatidylcholines (PC), and phosphatidylserines (PS), in different molar ratios, were delivered to the outer leaflet to study the effects of different lipid headgroups on RBC-nanoparticle interactions. Delivery of the phospholipids to the RBC membrane was confirmed using fluorescence microscopy and thin layer chromatography. RBC hemolysis after interaction with nanoparticles was measured as an indicator of membrane perturbation. Fluorescence anisotropy of the RBC membrane was also used to show how the lipid packing changes after lipid exchange and during interactions with nanoparticles, while flow cytometry was utilized as a measure of binding of nanoparticles to the RBCs. The results showed high disruption of RBCs when the outer leaflet consisted solely of SM or PC. In contrast, when PS was the sole constituent of the outer leaflet, nanoparticle disruption of the cells was negligible. These results are important in understanding the role of membrane lipid composition in cell-material interactions.