Transmembrane Difference in Colloid Osmotic Pressure Affects the Lipid Membrane Fluidity of Liposomes Encapsulating a Concentrated Protein Solution
Transmembrane Difference in Colloid Osmotic Pressure Affects the Lipid Membrane Fluidity of Liposomes Encapsulating a Concentrated Protein Solution
复制标题
DOI：
10.1021/acs.langmuir.6b04643
复制
发表时间：
2017-02-14
期刊：
影响因子：
3.9
通讯作者：
Sakai, Hiromi
中科院分区：
文献类型：
--
作者：
Kure, Tomoko;Sakai, Hiromi
血红蛋白囊泡(HB-V)是一种人工氧气载体，将高浓度的血红蛋白溶液(40g/dL)包裹在脂质体中。HB-V混悬液作为输血替代品的体内安全性和有效性以及储存期间的结构稳定性已被广泛研究。由于脂质体Hb水溶液的胶体渗透压(COP，200-300Torr)远高于血浆渗透压(20-25Torr)，因此脂膜是否能感觉到COP的跨膜差异是一个问题。我们用荧光偏振技术检测了膜的微粘度。为了避免红色Hb对荧光测定的干扰，我们用人血清白蛋白(HSA)代替Hb。根据浓度的不同，HSA和HB溶液都表现出高COP。将人血清白蛋白溶液(40g/dL)包埋在脂质体中，可在较低温度下降低膜的微粘度(25℃时为949+/-8cp->；60710cp)。结果表明，随着球表面积的增大，人血清白蛋白引起的跨膜渗透应力使脂质体最大限度地膨胀，膜的流动性也大大增加。即使在这样的条件下，最低的膜微粘度，在60℃时为377+/-10cp，远远高于1，2-dipalmitoyl-sn-glycero-3-phosphatidylcholine脂质体(60℃时为40+/-2cp)。因此，HB-V和HSA-V在高COP引起的跨膜应力下保持球形结构和机械稳定性，如文献所述。
A hemoglobin vesicle (Hb-V) is an artificial oxygen carrier encapsulating a highly concentrated hemoglobin solution (40 g/dL) in a liposome. The in vivo safety and efficacy of Hb-V suspension as a transfusion alternative and structural stability during storage have been studied extensively. Because the intraliposomal Hb aqueous solution can possess colloid osmotic pressure (COP, 200-300 Torr) that is much higher than that of blood plasma (20-25 Torr), a question arises as to whether the lipid membrane senses the transmembrane difference in COP. We examined the membrane microviscosity using a fluorescence polarization technique. To avoid the interference of red Hb on the fluorescence measurement, we used human serum albumin (HSA) as a substitute for Hb. Both HSA and Hb solutions show high COP depending on the concentration. Encapsulation of HSA solution (40 g/dL) in the liposome decreased the membrane microviscosity at a lower temperature (949 +/- 8 cP -> 607 10 cP at 25 degrees C). The result indicates that the transmembrane osmotic stress induced by HSA encapsulation expands the liposome maximally with increasing spherical surface area, and the membrane fluidity is increased extremely. Even for such a condition, the lowest membrane microviscosity, 377 +/- 10 cP at 60 degrees C, is much higher than that of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine liposome (40 +/- 2 cP at 60 degrees C). Accordingly, Hb-V as well as HSA-V maintains a spherical structure and mechanical stability under transmembrane stress caused by high COP, as described in the literature.