RANGE AND MAGNITUDE OF THE STERIC PRESSURE BETWEEN BILAYERS CONTAINING PHOSPHOLIPIDS WITH COVALENTLY ATTACHED POLY(ETHYLENE GLYCOL)
RANGE AND MAGNITUDE OF THE STERIC PRESSURE BETWEEN BILAYERS CONTAINING PHOSPHOLIPIDS WITH COVALENTLY ATTACHED POLY(ETHYLENE GLYCOL)
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DOI：
10.1016/s0006-3495(95)80369-3
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发表时间：
1995-05-01
影响因子：
3.4
通讯作者：
MCINTOSH, TJ
中科院分区：
文献类型：
--
作者：
KENWORTHY, AK;HRISTOVA, K;MCINTOSH, TJ
含有共价连接的聚乙二醇（PEG-脂质）的磷脂的脂质体的相互作用特性引起了人们的兴趣，因为此类脂质体正在被开发为药物递送载体，并且也是用于测量表面接枝聚合物特性的理想模型系统。对于含有 PEG 分子量为 350、750、2000 和 5000 的 PEG-脂质的双层，通过对施加已知渗透压的脂质体进行 X 射线衍射分析来测量压力-距离关系。对于给定的 PEG-脂质的每个浓度，相邻双层之间的距离随着施加压力的增加而单调减小。尽管对于含有 PEG-350 和 PEG-750 的双层来说，静电排斥对双层间相互作用的贡献是显着的，但对于含有 PEG-2000 和 PEG-5000 的双层来说，双层之间的主要排斥压力是由于附着的 PEG 造成的空间压力。该空间压力的范围和大小随着PEG-脂质浓度和PEG尺寸的增加而增加，并且在最大PEG-脂质浓度下PEG从双层表面的延伸长度强烈依赖于PEG的尺寸，对于PEG-750小于35埃，对于PEG-2000大约65埃，对于PEG-5000大约115埃。测得的压力-距离关系已根据表面接枝聚合物产生的空间压力的当前理论（deGennes，1987；Milner 等，1988b）进行了建模，我们对此进行了修改，以考虑聚合物多分散性的影响以及在低接枝密度下，来自并置双层表面的聚合物可以相互渗透或叉指的可能性。没有一种理论方案足以解释所有的实验结果。然而，对于给定的压力状态、PEG-脂质尺寸和PEG-脂质表面密度，适当修改的理论处理给出了对压力-距离数据的合理拟合。
The interactive properties of liposomes containing phospholipids with covalently attached poly(ethylene glycol) (PEG-lipids) are of interest because such liposomes are being developed as drug delivery vehicles and also are ideal model systems for measuring the properties of surface-grafted polymers. For bilayers containing PEG-lipids with PEG molecular weights of 350, 750, 2000, and 5000, pressure-distance relations have been measured by X-ray diffraction analysis of liposomes subjected to known applied osmotic pressures. The distance between apposing bilayers decreased monotonically with increasing applied pressure for each concentration of a given PEG-lipid. Although for bilayers containing PEG-350 and PEG-750 the contribution of electrostatic repulsion to interbilayer interactions was significant, for bilayers containing PEG-2000 and PEG-5000 the major repulsive pressure between bilayers was a steric pressure due to the attached PEG. The range and magnitude of this steric pressure increased both with increasing PEG-lipid concentration and PEG size, and the extension length of the PEG from the bilayer surface at maximum PEG-lipid concentration depended strongly on the size of the PEG, being less than 35 Angstrom for PEG-750, and about 65 Angstrom for PEG-2000 and 115 Angstrom for PEG-5000. The measured pressure-distance relations have been modeled in terms of current theories (deGennes, 1987; Milner et al., 1988b) for the steric pressure produced by surface-grafted polymers, as modified by us to take into account the effects of polymer polydispersity and the possibility that, at low grafting densities, polymers from apposing bilayers surfaces can interpenetrate or interdigitate. No one theoretical scheme is sufficient to account for all the experimental results. However, for a given pressure regime, PEG-lipid size, and PEG-lipid surface density, the appropriately modified theoretical treatment gives a reasonable fit to the pressure-distance data.