Thermodynamics of interaction between carbohydrates and unilamellar dipalmitoyl phosphatidylcholine membranes

The purpose of this study was to examine the direct effect of sucrose and sucralose on the main phase transition of dipalmitoyl phosphatidylcholine (DPPC) liposomes with differential scanning calorimetry, for use as potential cryopreservatives for cells. Because cells are typically treated directly with cryopreservatives and not thermally cycled to erase thermal history, we have focused on the impact that these sugars have on the main phase transition during the first heating and cooling cycles. The incorporation of sucrose appears to have very little effect on the phase behavior of DPPC liposomes except a broadening of the main phase transition. In contrast, sucralose leads to a drop in the transition peak temperature from 41.5 to 39.6 °C when there is 50 mol% sucralose present. Further increases in sucralose concentration result in the peak transition temperature gradually increasing again to 41.1 °C at 87 mol% sugar. This change is accompanied by decrease in the width of the transition, during heating, as well as increased hysteresis. This phenomenon may be due to a kosmotropic effect resulting in partial dehydration and interdigitation of the bilayer as the sucralose concentration is increased. These findings indicate that sucralose may be useful for the cryopreservation of cell membranes.