Reversible Control of Spacing in Charged Lamellar Membrane Hydrogels by Hydrophobically Mediated Tethering with Symmetric and Asymmetric Double-End-Anchored Poly(ethylene glycol)s
Reversible Control of Spacing in Charged Lamellar Membrane Hydrogels by Hydrophobically Mediated Tethering with Symmetric and Asymmetric Double-End-Anchored Poly(ethylene glycol)s
复制标题
通过对称和不对称双端锚定聚乙二醇疏水介导的束缚可逆控制带电层状膜水凝胶中的间距
DOI：
10.1021/acsami.8b16456
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发表时间：
2018
影响因子：
9.5
通讯作者：
Safinya, Cyrus R.
中科院分区：
文献类型：
--
作者：
Liu, Chenyu;Ewert, Kai K.;Wonder, Emily;Kohl, Phillip;Li, Youli;Qiao, Weihong;Safinya, Cyrus R.
复杂材料通常通过经由竞争和/或协同相互作用的结构单元的分级组装来实现其显著的功能特性。在这里，我们描述了新的双端锚定的聚（乙二醇）（DEA-PEG）-大分子的性质，旨在赋予疏水介导的束缚带电荷的脂质膜之间的吸引力。我们合成了具有两个双尾（对称）或一个双尾和一个单尾（不对称）疏水末端锚的DEA-PEG（MW 2000（2K）和4.6K），并使用小角X射线散射表征了它们的平衡和动力学性质。不含和含PEG脂质的对照多层膜（即，单端锚定的PEG）连续溶胀，由于静电以及在PEG脂质的情况下的空间排斥，层间距在30 - 90重量%水含量之间增加。相比之下，含有DEA-PEG的层状膜水凝胶中的层间距在有限的水稀释范围内扩大并达到“锁定”状态，其显示出接近恒定的膜壁间距（δw），并且进一步增加水含量。值得注意的是，对于2K和4.6K PEG，锁定状态与PEG的回转半径δw均为1.6RG。然而，δ w显著小于PEG的物理尺寸（2（5/3）1/2 RG）是非常出乎意料的，并且意味着与游离PEG相比，PEG系链在两端的锚定导致限制在层之间的PEG构象的相当大的变形。值得注意的是，层状水凝胶可以被设计成通过改变DEA-PEG浓度从锁定状态可逆地转变为解锁状态（膜未结合），从而控制由于桥接构象引起的层间吸引力的强度。DEA-PEG的研究结果对疏水介导的脂质或表面活性剂包被的结构单元在水性环境中以可预测的间距具有不同的形状和大小的组装具有广泛的影响。
Complex materials often achieve their remarkable functional properties by hierarchical assembly of building blocks via competing and/or synergistic interactions. Here, we describe the properties of new double-end-anchored poly(ethylene glycol)s (DEA-PEGs)—macromolecules designed to impart hydrophobically mediated tethering attractions between charged lipid membranes. We synthesized DEA-PEGs (MW 2000 (2K) and 4.6K) with two double-tail (symmetric) or a double-tail and a single-tail (asymmetric) hydrophobic end anchors and characterized their equilibrium and kinetic properties using small-angle X-ray scattering. Control multilayer membranes without and with PEG lipid (i.e., single-end-anchored PEG) swelled continuously, with the interlayer spacing increasing between 30 and 90 wt % water content due to electrostatic as well as, in the case of PEG lipid, steric repulsion. In contrast, interlayer spacings in lamellar membrane hydrogels containing DEA-PEGs expanded over a limited water dilution range and reached a “locked” state, which displayed a near constant membrane wall-to-wall spacing (δw) with further increases in water content. Remarkably, the locked state displays a simple relation to the PEG radius of gyration δw≈ 1.6RGfor both 2K and 4.6K PEG. Nevertheless, δwbeing considerably less than the physical size of PEG (2(5/3)1/2RG) is highly unexpected and implies that, compared to free PEG, anchoring of the PEG tether at both ends leads to a considerable distortion of the PEG conformation confined between layers. Significantly, the lamellar hydrogel may be designed toreversiblytransition from a locked to an unlocked (membrane unbinding) state by variations in the DEA-PEG concentration, controlling the strength of the interlayer attractions due to bridging conformations. The findings with DEA-PEGs have broad implications for hydrophobic-mediated assembly of lipid- or surfactant-coated building blocks with distinct shape and size, at predictable spacing, in aqueous environments.