The effect of cholesterol (CHOL) content on the permeability and fluidity of dipalmitoylphosphatidylcholine (DPPC) liposome membrane was investigated. Liposomes encapsulating sulforhodamine B (SRB), a fluorescent dye, were prepared by reverse phase evaporation technique (REV) at various DPPC:CHOL molar ratios (from 100:0 to 100:100). The release kinetics of SRB was studied during 48 h in buffer (pH 7.4) containing NaCl at 37 °C. The DPPC:CHOL formulations were also characterized for their size, polydispersity index and morphology. Increasing CHOL concentration induced an increase in the mean liposomes size accompanying with a shape transition from irregular to nanosized, regular and spherical vesicles. The release kinetics of SRB showed a biphasic pattern; the release data was then analyzed using different mathematical models. On the overall, the SRB release was governed by a non-Fickian diffusion during the first period (0–10 h) while it followed a Fickian diffusion between 10 and 48 h. Changes in DPPC liposome membrane fluidity of various batches (CHOL% 0, 10, 20, 30 and 100) were monitored by using 5- and 16 doxyl stearic acids (DSA) as spin labels. CHOL induced a decrease in the bilayer fluidity. Concisely, CHOL represents a critical component in modulating the release of hydrophilic molecules from lipid vesicles.

研究了胆固醇（CHOL）含量对二棕榈酰磷脂酰胆碱（DPPC）脂质体膜渗透性和流动性的影响。通过反相蒸发技术（REV）以各种DPPC：CHOL摩尔比（从100：0到100：100）制备封装荧光染料磺基若丹明B（SRB）的脂质体。在含有NaCl的缓冲液（pH 7.4）中，在37°C下48小时内研究了SRB的释放动力学。还对DPPC：CHOL配方的大小，多分散指数和形态进行了表征。CHOL浓度的增加导致平均脂质体大小增加，并伴随着形状从不规则到纳米，规则和球形囊泡的转变。SRB的释放动力学呈两相模式。然后使用不同的数学模型分析释放数据。总的来说，在第一个时期（0-10小时），SRB的释放受非菲克扩散的控制，而在10到48小时之间，菲克扩散的发生则由非菲克扩散控制。通过使用5和16个二甲苯基硬脂酸（DSA）作为旋转标记来监测各个批次（CHOL％0、10、20、30和100）的DPPC脂质体膜流动性的变化。CHOL导致双层流动性降低。简而言之，CHOL代表了调节亲水分子从脂质囊泡释放的关键成分。