Effects of carbon chain difference and lipid composition on the contact mechanics of two-component vesicle

The composition of phospholipid mixture is known to influence the lateral organization of the resulting biomembrane. In this study, the substrate-induced adhesion of two component vesicles composed of dimyristoyl-phosphatidylcholine/distearoyl-phosphatidylcholine (DMPC/DSPC) is probed by confocal reflectance interference microscopy (C-RICM), cross-polarized light microscopy and contact mechanics modeling. First, our contact mechanics model of adherent vesicle is validated for the two-component DMPC/DSPC vesicles. The incorporation of 10 mol% of DSPC in DMPC bilayer enhances both the degree of vesicle deformation and adhesion energy of the resulting two-component vesicle in comparison with those of one-component DMPC or DSPC vesicles. It is further illustrated that the compositional variation of the binary DMPC/DSPC mixture does not affect the contact mechanics parameters of adherent vesicles when the mole fraction of DSPC increases from 0 to 70%. Interestingly, the difference in the acyl chain length between the two lipids within the phospholipid mixture is directly correlated with the degree of vesicle deformation and adhesion energy. Overall, the biophysical responses of adherent vesicles are shown to be tunable by the bio-membrane composition and the carbon chain difference.