Despite recent advances in the supramolecular assembly of cell-penetrating peptide (CPP) nanostructures, the tuning of size, shape, morphology and packaging of drugs in these materials still remain unexplored. Herein, through sequential ligation of peptide building blocks, we create cell-penetrating self-assembling peptide nanomaterials (CSPNs) with the capability to translocate inside cells. We devised a triblock array of Tat48-59 [HIV-1 derived transactivator of transcription48-59] based CPPs, conjugated to up to four Phenylalanine (Phe) residues through an amphiphilic linker, (RADA)2. We observed that the sequential addition of Phe leads to the transition of CSPN secondary structures from a random coil, to a distorted α-helix, a β-sheet, or a pure α-helix. This transition occurs due to formation of a heptad by virtue of even number of Phe. Atomic force microscopy revealed that CSPNs form distinct shapes reminiscent of a "drill-bit". CSPNs containing two, three or four Phe, self-assemble into "nanodrill-like structures" with a coarse-twisted, non-twisted or fine-twisted morphology, respectively. These nanodrills had a high capacity to encapsulate hydrophobic guest molecules. In particular, the coarse-twisted nanodrills demonstrate higher internalization and are able to deliver rapamycin, a hydrophobic small molecule that induced autophagy and are capable of in vivo delivery. Molecular dynamics studies provide microscopic insights into the structure of the nanodrills that can contribute to its morphology and ability to interact with cellular membrane. CSPNs represent a new modular drug delivery platform that can be programmed into exquisite structures through sequence-specific fine tuning of amino acids.

中文翻译：

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用于细胞内递送的纳米钻样结构的超分子自组装。

尽管在细胞穿透肽（CPP）纳米结构的超分子组装方面取得了最新进展，但是在这些材料中药物的大小，形状，形态和包装的调整仍未探索。在本文中，通过肽基结构单元的顺序连接，我们创建了具有穿透细胞能力的自组装肽纳米材料（CSPNs），具有在细胞内部转运的能力。我们设计了一个三嵌段阵列的Tat48-59 [HIV-1衍生的转录48-59转录反式激活子]基的CPP，通过两亲性接头（RADA）2与多达四个苯丙氨酸（Phe）残基偶联。我们观察到，Phe的顺序添加导致CSPN二级结构从随机线圈过渡到扭曲的α螺旋，β折叠或纯α螺旋。由于借助偶数Phe形成了七肽，因此发生了这种转变。原子力显微镜显示，CSPNs形成独特的形状，让人联想到“钻头”。包含两个，三个或四个Phe的CSPN分别自组装成具有粗捻，非捻或细捻形态的“纳米钻状结构”。这些纳米钻具有高封装疏水性客体分子的能力。特别地，粗扭曲的纳米钻表现出更高的内在化，并且能够递送雷帕霉素，雷帕霉素是一种疏水性小分子，其诱导自噬并且能够体内递送。分子动力学研究提供了对纳米钻结构的微观见解，这些纳米钻可以有助于其形态和与细胞膜相互作用的能力。