Partitioning of Fullerene Between Water and Synthetic Membrane Materials: Effects of Temperature and Membrane Compositions

Carbon fullerene (C₆₀) is one of the most common nanomaterials used in various applications. In this study, the partitioning of fullerenes between water and synthetic membrane vesicles (K_lipw) is investigated using lipid bilayers supported on nonporous micro silica bead. K_lipw values are measured with various types of lipid membrane vesicles and temperatures. Lipids used in this study are 1,2 dioleoyl-sn-glycero-3 phosphocholine (DOPC), 1,2 dimyristoyl-sn-glycero-3-phosphochloline (DMPC), 1,2 dierucoyl-sn-glycero-3-phosphochloline (DEruPC), DOPC/sphinogosylphosphochloline (SM)/cholesterol, DMPC/SM/cholesterol, DEruPC/SM/cholesterol.  Each lipid has a different transition temperature (T_m). Ternary lipid (liquid ordered phase lipid, liquid disordered phase lipid and cholesterol) mixture membrane vesicles are prepared at two different temperatures (above and below T_m), and vesicles kept at above T_m can undergo lateral phase separation. K_lipw values depend on the temperature and types of lipids, indicating that the fluidity of the lipid bilayer affects the distribution of fullerene between water and lipid membranes. In addition, K_lipw values of fullerene for ternary lipid mixture membrane vesicles prepared at above transition temperature (T_m) are higher than those prepared at below T_m. This result suggests that the K_lipw is influenced by the phase height difference between liquid disordered lipid and liquid ordered lipid/cholesterol, which is created after the phase separation. Therefore, phase transition and compositions of lipid membrane vesicles are of critical importance in evaluating the transport and bioconcentration of fullerenes.