Kapitza Susanne B, Michel Bettina R, van Hoogevest Peter, Leigh Mathew L S, Imanidis Georgios
Institute of Pharmaceutical Technology, University of Basel, Basel, Switzerland.
Eur J Pharm Biopharm. 2007 Apr;66(1):146-58. doi: 10.1016/j.ejpb.2006.08.010. Epub 2006 Aug 23.
The purpose of this work was to determine the influence of liposomal solubilization of poorly water soluble drugs exhibiting apical efflux on permeation kinetics and cell toxicity in Caco-2 cells. The HIV-protease inhibitors indinavir and saquinavir were incorporated in phosphatidylcholine liposomes at maximal drug-to-lipid mass ratios and their absorption was determined in Caco-2 cell cultures grown on Transwell inserts using purely aqueous drug solutions as reference. A novel mathematical model was developed to quantitatively delineate the contribution of passive membrane permeation and carrier mediated efflux to transport across the cell monolayer and passive permeability coefficient and maximal efflux rate and affinity constant of the transporter system were determined. Cell toxicity of phospholipids was evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and the lactate dehydrogenase (LDH) assay. Cell integrity was not significantly affected by phospholipid concentrations of up to 150 mg/ml with respect to the used standard tests. Maximum drug concentration was increased 10- and 750-fold for indinavir and saquinavir, respectively, by the use of liposomes. The passive membrane permeability coefficient differed between the two drugs in accordance with their lipophilicity and the affinity for apical efflux transporters was on average 4-fold greater for saquinavir than for indinavir. Liposomal solubilization diminished the passive permeability coefficient of both drugs but the passive apical-to-basal delivery rate was increased by the liposomes compared to the purely aqueous solutions at maximal donor concentrations for at least one of the two drugs. Efflux rate reached a maximum for the liposomal formulations reflecting transporter saturation. Hence, liposomal solubilization considerably increased drug concentration in the media and altered absorption behavior by affecting both the passive diffusion and the carrier mediated efflux components of cell monolayer permeation.
本研究旨在确定脂质体增溶对具有顶端外排作用的难溶性药物在Caco-2细胞中的渗透动力学和细胞毒性的影响。将HIV蛋白酶抑制剂茚地那韦和沙奎那韦以最大药物与脂质质量比掺入磷脂酰胆碱脂质体中，并以纯水溶液药物溶液为对照，在Transwell小室上生长的Caco-2细胞培养物中测定其吸收情况。开发了一种新型数学模型，以定量描述被动膜渗透和载体介导的外排在跨细胞单层转运中的作用，并确定了被动渗透系数、转运体系统的最大外排速率和亲和常数。通过3-(4,5-二甲基噻唑-2-基)-2,5-二苯基-2H-四唑溴盐(MTT)和乳酸脱氢酶(LDH)测定法评估磷脂的细胞毒性。就所使用的标准测试而言，高达150 mg/ml的磷脂浓度对细胞完整性没有显著影响。使用脂质体后，茚地那韦和沙奎那韦的最大药物浓度分别提高了10倍和750倍。两种药物的被动膜渗透系数因其亲脂性而异，沙奎那韦对顶端外排转运体的亲和力平均比茚地那韦高4倍。脂质体增溶降低了两种药物的被动渗透系数，但与两种药物中至少一种在最大供体浓度下的纯水溶液相比，脂质体增加了被动顶端到基底的递送速率。脂质体制剂的外排速率达到最大值，反映了转运体的饱和。因此，脂质体增溶通过影响细胞单层渗透的被动扩散和载体介导的外排成分，显著提高了培养基中的药物浓度并改变了吸收行为。
