Self-Assembly of Thermally Responsive Amphiphilic Diblock Copolypeptides into Spherical Micellar Nanoparticles
Self-Assembly of Thermally Responsive Amphiphilic Diblock Copolypeptides into Spherical Micellar Nanoparticles
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DOI：
10.1002/anie.201001356
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发表时间：
2010-01-01
影响因子：
16.6
通讯作者：
Chaikof, Elliot L.
中科院分区：
文献类型：
--
作者：
Kim, Wookhyun;Thevenot, Julie;Chaikof, Elliot L.
随着蛋白质自组装的结构-性质关系得到阐明，化学和结构生物学的进步通过化学和生物合成方案促进了生物启发多肽的开发，这些方案提供了新型蛋白质基薄膜、纤维、胶束和凝胶。[1-3]在许多情况下，可逆蛋白质自组装是由响应外部刺激诱导的肽单元的明确构象变化驱动的。[4, 5]事实上，设计的分子组装刺激响应肽已成为一种“自下而上”的方法，用于从简单的氨基酸构建模块创建复杂但有序的分层结构。 [6]正如二嵌段和三嵌段多肽的设计所示，微米和纳米级特征可以通过控制肽的氨基酸序列、分子量和二级结构来调节。[5,7,8]特别是，两亲性嵌段共聚肽可以自组装成各种不同的结构，包括棒状、圆柱状、球状和囊泡。[2,5]尽管由化学和构象独特的单个多肽嵌段组成的二嵌段共聚物已被广泛应用。通过化学和生物合成方案生产，迄今为止，已经合成了相对较少的重组两亲性二嵌段多肽。[2,5b,8]考虑到整合靶向配体、细胞膜融合序列、受体激活肽、荧光或螯合基团的能力，以及定制药代动力学、生物分布和肽稳定性的能力，由重组蛋白嵌段共聚物产生的胶束或囊泡存在重大机会。基于五聚重复序列 (Val-Pro-Gly-Xaa-Gly) 的弹性蛋白模拟多肽在水溶液中经历热和 pH 响应性自组装。 [8, 9] 多肽的自发相分离与高于由五肽重复中第四个氨基酸 (Xaa) 的化学特性确定的独特转变温度 (Tt) 的局部二级结构的构象重排相一致。最近的研究证明了源自弹性蛋白的工程材料在广泛的生物医学和生物技术应用中的潜力，特别是药物输送。 [5b, c, 7, 8] 典型地，在第四个氨基酸位置上含有疏水性氨基酸（例如酪氨酸）的弹性蛋白模拟块在远低于 378°C 的温度下表现出从无规卷曲到重复型 II β 转角的构象转变，而在第四个氨基酸位置上含有带电氨基酸的块则表现出从无规卷曲到重复型 II β 转角的构象转变。 [9d, 10] 因此，我们假设 N 端和 C 端分别带有谷氨酸和酪氨酸残基的两亲性二嵌段共聚物将通过温度诱导的具有核壳结构的自组装来促进胶束的形成。此外，我们推测，在谷氨酸单元密度足够高的情况下，电荷排斥将限制亲水性嵌段的缔合并最大限度地减少胶束聚集。仅通过自组装稳定的胶束通常在含有天然存在的两亲物（例如血浆蛋白、糖脂和脂肽）的复杂环境中不稳定。因此，通过在块之间定位半胱氨酸残基，我们假设通过二硫键交联的纳米颗粒稳定化可以避免高分子量蛋白质聚集或不受控制的胶束-胶束缔合。这些研究代表了热响应和交联稳定蛋白质的第一份报告……
As structure–property relationships for protein self-assembly have been elucidated, advances in chemistry and structural biology have facilitated the development of biologically inspired polypeptides through chemical and biosynthetic schemes that have afforded novel protein-based films, fibers, micelles, and gels.[1–3] In a number of instances, reversible protein self-assembly has been driven by welldefined conformational changes of peptide units induced in response to an external stimulus.[4, 5] Indeed, designed molecular assembly of stimuli-responsive peptides has emerged as a “bottom-up” approach for creating complex, but ordered, hierarchical structures from simple amino acid building blocks.[6] As illustrated by the design of di-and triblock polypeptides, micro-and nanoscale features can be tuned by control of the amino acid sequence, molecular weight, and secondary structure of the peptide.[5, 7, 8] In particular, amphiphilic block copolypeptides can self-assemble into a variety of diverse structures, including rods, cylinders, spheres, and vesicles.[2, 5] Although diblock copolymers consisting of chemically and conformationally distinctive individual polypeptide blocks have been produced by chemical and biosynthetic schemes, to date, relatively few recombinant amphiphilic diblock polypeptides have been synthesized.[2, 5b, 8] Given the capacity to incorporate targeting ligands, cell membrane fusion sequences, receptor activating peptides, fluorescent or chelating groups, as well as the ability to tailor pharmacokinetics, biodistribution, and peptide stability, significant opportunities exist for micelles or vesicles produced from recombinant protein block copolymers. Elastin-mimetic polypeptides based on the pentameric repeat sequence (Val-Pro-Gly-Xaa-Gly) undergo thermal and pH-responsive self-assembly in aqueous solution.[8, 9] Spontaneous phase separation of the polypeptide coincides with a conformational rearrangement of local secondary structure above a unique transition temperature (Tt) determined by the chemical identity of the fourth amino acid (Xaa) in the pentapeptide repeat. Recent studies have demonstrated the potential of engineered materials derived from elastin in a broad range of biomedical and biotechnological applications and, in particular, drug delivery.[5b, c, 7, 8] Characteristically, elastin-mimetic blocks that contain hydrophobic amino acids in the fourth amino acid position, such as tyrosine, display a conformational transition from random coil to repetitive type II β turns at temperatures well below 378C, whereas blocks that contain a charged amino acid in this position, such as glutamic acid, persist as a random coil throughout the physiologic temperature range.[9d, 10] Thus, we postulated that amphiphilic diblock copolymers bearing glutamic acid and tyrosine residues in N-and C-terminal blocks, respectively, would promote micelle formation by temperature-induced self-assembly with a core–shell structure. Moreover, we speculated that at a sufficiently high density of glutamic acid units, charge repulsion would limit the association of the hydrophilic blocks and minimize micelle aggregation. Micelles stabilized by self-assembly alone are typically unstable in a complex environment containing naturally occurring amphiphiles, such as plasma proteins, glycolipids, and lipopeptides. Therefore, by positioning cysteine residues between blocks, we hypothesized that highmolecular-weight protein aggregation or uncontrolled micelle–micelle association would be avoided by nanoparticle stabilization through disulfide cross-linking. These studies represent the first report of thermally responsive and crosslink stabilized protein …