Chihiro Kaise

Preparation of liposomes containing Ceramide 3 and their membrane characteristics.

Liposomes composed of Ceramide 3, [2S,3S,4R-2-stearoylamide-1,3,4-octadecanetriol], and L-alpha-dipalmitoylphosphatidylcholine (DPPC) were prepared by varying the amount of Ceramide 3, and the effects of Ceramide 3 on the liposome formation, particle size, dispersibility, microviscosity and phase transition temperature were examined by means of a microscopy, a dynamic light scattering method, a fluorescence polarization method, a differential scanning calorimetry (DSC) and so on. All the DPPC was able to contribute to the formation of liposomes up to 0.130 mol fraction of Ceramide 3. The particle size of liposomes was almost unaffected by the addition of Ceramide 3. The dispersibility of liposomes containing Ceramide 3 was maintained for at least 15 days. The microviscosity of liposomal bilayer membranes in the liquid crystalline state was increased with increasing the mole fraction of Ceramide 3, while that in the gel state was independent of the mole fraction of Ceramide 3. The phase transition temperature from gel to liquid crystalline states of DPPC bilayer membranes was shifted upwards with the addition of Ceramide 3, indicating a cooperative interaction between DPPC and Ceramide 3 molecules. However, a sharp DSC peak became broad and split at higher mole fractions of Ceramide 3, suggesting a phase separation in the mixed DPPC/Ceramide 3 liposomal bilayer membranes. These phenomena were suggested to be related to the previously observed fact for the mixed DPPC/Ceramide 3 monolayers that Ceramide 3 interacts with DPPC in the liquid-expanded phase with consequent phase separation accompanied with domain formation.

Effects of β-Sitosteryl Sulfate on the Hydration Behavior of Dipalmitoylphosphatidylcholine

We investigated the hydration behavior of dipalmitoylphosphatidylcholine (DPPC) bilayers containing sodium β-sitosteryl sulfate (PSO4). PSO4 was found to enhance hydration in the headgroup region of DPPC bilayers. Therefore, with the incorporation of PSO4 into DPPC membranes, the amount of water required to reach the fully hydrated state was enhanced as indicated by the constant values of the main phase transition temperature (Tm) and the bilayer repeat distance (d). For example, with the addition of 20 mol% of PSO4, the saturation point was shifted to ~70 wt% water compared to ~40 wt% for pure DPPC and 47 wt% for DPPC-cholesterol. The effectiveness of PSO4 in fluidizing the membrane and enhancing its hydration state can be useful in the pharmaceutical and cosmetic industries.

Effects of β-Sitosteryl Sulfate on the Phase Behavior and Hydration Properties of Distearoylphosphatidylcholine: a Comparison with Dipalmitoylphosphatidylcholine

We have studied the phase behavior of distearoylphosphatidylcholine (DSPC) in the presence of sodium β-sitosteryl sulfate (PSO4). PSO4 was found to induce sterol-rich and sterol-poor domains in the DSPC membrane. These two domains constitute a fluid, liquid ordered (Lo) phase and a gel (Lβ) phase. PSO4 was less miscible in DSPC than in a dipalmitoylphosphatidylcholine (DPPC) membrane, as evidenced by its tendency to separate from the bilayer at a concentration of 50 mol%. This lack of miscibility was attributed to the greater van der Waals forces between the PC hydrocarbon chains. In addition to affecting the phase behavior, PSO4 also enhanced the hydration of the membrane. Despite its weaker interaction with DSPC compared to DPPC, its tendency to fluidize this phospholipid and enhance its hydration can be useful in formulating cosmetics and pharmaceutical products.

Effects of sodium β-sitosteryl sulfate on the phase behavior of dipalmitoylphosphatidylcholine

We have studied the phase behavior of dipalmitoylphosphatidylcholine (DPPC) containing sodium β-sitosteryl sulfate (PSO4). PSO4 was found to lower the phase transition temperature of DPPC to a higher degree than cholesterol or β-sitosterol. It also gave rise to the formation of a modulated (ripple) phase (Pβ) at low to moderate concentrations. At concentrations greater than 25 mol%, it completely changed the membrane into a fluid phase. This shows that PSO4 is capable of disordering the hydrocarbon chains of PC efficiently. The characteristics of PSO4 for fluidizing the membrane can be useful for the pharmaceutical and cosmetics industries.