Thermally and photochemically triggered self-assembly of peptide hydrogels
Thermally and photochemically triggered self-assembly of peptide hydrogels
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DOI：
10.1021/ja011535a
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发表时间：
2001-09-26
影响因子：
15
通讯作者：
Messersmith, PB
中科院分区：
文献类型：
--
作者：
Collier, JH;Hu, BH;Messersmith, PB
自组装系统提供了有吸引力的平台，工程刺激响应材料与控制纳米和微观结构。最近设计这种系统的努力包括合成嵌段共聚物，通过亮氨酸拉链基序自组装成水凝胶的1a蛋白质，自组装成纳米管的1b环肽，1c-e和形成纤维状β-折叠网络的肽。1f-i在这里，我们展示了响应于热或光化学触发从流体前体自组装成高度交联的肽水凝胶的系统。我们的系统利用刺激响应性释放的封装盐从脂质体触发自组装的16个氨基酸的肽。我们表明，通过温和加热或暴露于近红外光诱导自组装导致肽/脂质体悬浮液快速凝胶化成高度交联的纤维状β-折叠水凝胶。通过生理良性刺激（温度、光）触发肽溶液的快速溶胶-凝胶转化的能力可能导致用于药物递送、伤口愈合和组织工程应用的新的可注射材料的开发。16个氨基酸的肽由交替的疏水性和亲水性残基组成：H2 N-（FEFEFKFK）2-COOH，（FEK 16）。我们选择研究FEK 16，因为已知几种具有交替疏水-亲水残基的相关肽通常以离子强度依赖性方式自组装成β-折叠结构。1f，2 β-折叠结构受到肽的严格交替的疏水-亲水一级结构的青睐，其将所有疏水侧链定位在β-折叠的一侧，而将所有亲水侧链定位在另一侧。3盐诱导的这种肽的自组装可能是通过增加离子浓度屏蔽静电排斥力来驱动的，从而允许疏水吸引力和货车范德华力占主导地位。2d FEK 16的自组装特性与其他具有类似交替结构的肽相似。发现1f，1 i，2b FEK 16在纯水中高度可溶，但在mM浓度的NaCl、KCl和CaCl 2存在下形成自组装聚集体（FEK 16浓度> 10 mg/mL时的凝胶）。FEK 16（30 mg/mL）在D2 O和CaCl 2/D2 O中的FTIR光谱显示在1622和1694 cm-1处有强酰胺I吸收峰，在1525 cm-1处有酰胺II峰（参见IR光谱的支持信息），表明β-折叠结构含量较高。4a-b在1694 cm-1处的弱带表明β折叠是反平行的，尽管该峰也可能来自β转角或无序结构。4 b更详细的结构分析，如固态NMR光谱，将是必要的，以确认反平行构象。4c由CaCl 2添加诱导的自组装FEK 16的IR光谱与纯D2 O中的FEK 16的IR光谱几乎相同，表明FEK 16主要以液态的小β-折叠多聚体存在，并且凝胶形成涉及这些预先形成的β-折叠结构域的聚结/聚集。CD用于评估在H2O中β-折叠形成的浓度依赖性。证实FEK 16在高于10 μM的浓度下采用β-折叠构象，而低于该浓度时肽采用R-螺旋构象。在低肽浓度（< 10 μM）下，添加CaCl 2诱导FEK 16中的R-螺旋向β-折叠转变。(See CD光谱的支持信息）。
Self-assembling systems present attractive platforms for engineering stimulus-responsive materials with controlled nano-and microstructures. Recent efforts to design such systems include synthetic block copolymers, 1a proteins that self-assemble into hydrogels via leucine zipper motifs, 1b cyclic peptides that selfassemble into nanotubes, 1c-e and peptides that form fibrillar β-sheet networks. 1f-i Here we demonstrate systems that selfassemble from fluid precursors into highly cross-linked peptide hydrogels in response to thermal or photochemical triggering. Our system takes advantage of stimuli-responsive release of encapsulated salts from liposomes to trigger the self-assembly of a 16-amino acid peptide. We show that the induction of self-assembly by gentle warming or by exposure to near-infrared light results in rapid gelation of peptide/liposome suspensions into highly cross-linked, fibrillar, β-sheet hydrogels. The ability to trigger rapid sol-gel transformations of peptide solutions via physiologically benign stimuli (temperature, light) may lead to the development of new injectable materials for drug delivery, wound healing, and tissue engineering applications. The 16-amino acid peptide consists of alternating hydrophobic and hydrophilic residues: H2N-(FEFEFKFK) 2-COOH,(FEK16). We chose to investigate FEK16 because several related peptides with alternating hydrophobic-hydrophilic residues are known to self-assemble into β-sheet structures, often in an ionic-strengthdependent manner. 1f, 2 β-sheet structure is favored by the strictly alternating hydrophobic-hydrophilic primary structure of the peptide, which positions all hydrophobic side chains on one side of the β-sheet and all hydrophilic side chains on the other. 3 Saltinduced self-assembly of this peptide may be driven by the shielding of electrostatic repulsive forces with increasing ion concentrations, allowing attractive hydrophobic and van der Waals forces to dominate. 2dThe self-assembly characteristics of FEK16 were found to resemble those of other peptides with similar alternating structures. 1f, 1i, 2b FEK16 was found to be highly soluble in pure H2O but formed self-assembled aggregates (gels at FEK16 concentrations> 10 mg/mL) in the presence of mM concentrations of NaCl, KCl, and CaCl2. FTIR spectroscopy of FEK16 (30 mg/mL) in D2O and CaCl2/D2O revealed strong amide I absorption peaks at 1622 and 1694 cm-1 and an amide II peak at 1525 cm-1 (see Supporting Information for IR spectra), indicating a high content of β-sheet structure. 4a-b A weak band at 1694 cm-1 suggested that the β-sheet was antiparallel, although it is also possible for this peak to arise from β-turn or disordered structures. 4b More detailed structural analysis such as solid-state NMR spectroscopy will be necessary to confirm the antiparallel conformation. 4c The IR spectra of self-assembled FEK16 induced by CaCl2 addition was nearly identical to that of FEK16 in pure D2O, suggesting that FEK16 exists predominantly as small β-sheet multimers in the liquid state and that gel formation involves coalescence/aggregation of these preformed β-sheet domains. CD was utilized to assess the concentration dependence of β-sheet formation in H2O. It was confirmed that FEK16 adopted a β-sheet conformation at concentrations above 10 μM, whereas below this concentration the peptide adopted an R-helical conformation. At low peptide concentrations (< 10 μM), addition of CaCl2 induced an R-helix-to-β-sheet transition in FEK16.(See Supporting Information for CD spectra).