异氰酸苯酯诱导的类胶原多肽自组装

Collagen-like Peptide Self-Assembly via Phenyl Isocyanate Induction

在体外设计和构建多种仿生纳米材料是人类理解天然自组装机制的基础。胶原蛋白是动物体内含量最高的蛋白质,也是生物医用材料领域最常用的天然高分子之一。化学合成的类胶原多肽来源清洁、可设计性高,是理想的纳米生物基底材料。目前类胶原多肽自组装的策略多基于二硫键、静电引力,π–π堆叠,金属配位等单一作用力,鲜有利用有机小分子提供弱作用力诱发肽分子之间自组装。本研究利用有机分子4,4’-亚甲基双(异氰酸苯酯)修饰类胶原多肽的氮端,通过圆二色谱、动态光散射和原子力子显微镜等方法对组装体形成进行表征。研究结果显示4,4’-亚甲基双(异氰酸苯酯)不仅能够显著提高类胶原多肽折叠形成三股螺旋的热稳定性,还可促进其组装形成形貌规整的纳米纤维。本研究为类胶原多肽的组装提供了一种简单高效的新策略。

Synthetic matrices provide powerful tools for dissecting molecular interactions involved in the organization of the extracellular matrix(ECM),establishment of cell axis polarity,and suppression of neoplasticity in pre-cancerous endothelial cells.Collagen is the most abundant protein in extracellular matrix.A de novo approach is essential for the synthesis of collagen matrices which can have a broad impact on the understanding of matrix biology and our capacity to construct safe and medically useful biomaterials.Conventionally,the ECM has been studied by an analytical“top-down”approach,where the individual components of the matrix are first isolated and then characterized to explore their biochemical and functional properties.Since native collagen is difficult to modify and can engender pathogenic and immunological side effects,its application on tissue regeneration is limited.Therefore,we attempted to synthesize artificial collagen directly through small organic molecule recognition.The collagen-like peptides possess various benefits such as being clean,programmable,and easy to modify;therefore,in recent years,they have been used as ideal substrates for the synthesis of collagen nanomaterials.The self-assembly of collagen-like peptides is mainly driven by various non-covalent interactions such as electrostatic attraction,π–π stacking,and metal coordination.This renders a difficulty in the rational design of uniform nanostructures from short synthesized peptides and demands a novel strategy.To date,small organic molecules have been rarely used for the self-assembly of collagen-like peptides.In the present study,we attempted to use the small organic molecules for the combined supramolecular self-assembly of collagen-like peptides.Initially,the collagen-like peptides,(POG)_(6) and(POG)_(8),synthesized by the solid-phase synthesis technique,were both modified chemically using 4,4’-methylene bis(phenyl isocyanate)to obtain the collagen-like hybrid peptides,AP_(6) and AP_(8),respectively.Phenyl isocyanate contributes to the formation of potential weak forces,such as hydrogen bonds and π–π stacking at the N-terminal regions of the collagen-like hybrid peptides.The purity and molecular weight of the collagen-like hybrid peptides were analyzed using analytical high-performance liquid chromatography(HPLC)and matrixassisted laser desorption ionization time of flight(MALDI-TOF),respectively.The stability of AP_(6) and AP_(8) triple helices was analyzed by circular dichroism(CD)spectroscopy.The small organic molecule 4,4’-methylene bis(phenyl isocyanate)promoted the unfolding of(POG)_(6) and increased the melting temperature(Tm)of(POG)_(8) from 37.7 to 58.8℃ to form a triple helix.The hydrodynamic radii of collagen-like hybrid peptides were measured by dynamic light scattering(DLS).Atomic force microscopy(AFM)and transmission electron microscopy(TEM)were used to analyze the morphology of the aggregation states.AFM results showed that the collagen-like hybrid peptides,AP6 and AP8,formed nanofibers spontaneously.Consistent with the AFM results,TEM showed that the AP_(6) and AP_(8) collagen-like hybrid peptides also formed nanofiber structures.The formation of stable complexes was attributed to the presence of multiple weak interactions such as hydrogen bonding,π–π stacking,and hydrophobic interactions.In the present study,we demonstrated that the chemical modification of collagen-like polypeptides at the N-terminus via the small organic molecule,4,4’-methylene bis(phenyl isocyanate),promoted the intramolecular and intermolecular assembly of collagen-like peptides.A simple and effective strategy has been developed in this study to promote the self-assembly of collagen-like peptides.