Small synthetic peptides capable of crossing biological membranes represent valuable tools in cell biology and drug delivery. While several cell-penetrating peptides (CPPs) of natural or synthetic origin have been reported, no peptide is currently known to cross both cytoplasmic and outer embryonic membranes. Here, we describe a method to engineer membrane-permeating cyclic peptides (MPPs) with broad permeation activity by screening mRNA display libraries of cyclic peptides against embryos at different developmental stages. The proposed method was demonstrated by identifying peptides capable of permeating Drosophila melanogaster (fruit fly) embryos and mammalian cells. The selected peptide cyclo[Glut-MRKRHASRRE-K*] showed a strong permeation activity of embryos exposed to minimal permeabilization pretreatment, as well as human embryonic stem cells and a murine fibroblast cell line. Notably, in both embryos and mammalian cells, the cyclic peptide outperformed its linear counterpart and the control MPPs. Confocal microscopy and single cell flow cytometry analysis were utilized to assess the degree of permeation both qualitatively and quantitatively. These MPPs have potential application in studying and nondisruptively controlling intracellular or intraembryonic processes.

中文翻译：

---

通过 mRNA 展示发现膜渗透环肽。

能够穿过生物膜的小合成肽是细胞生物学和药物递送中的有价值的工具。虽然已经报道了几种天然或合成来源的细胞穿透肽（CPP），但目前已知没有肽能够穿过细胞质和胚胎外膜。在这里，我们描述了一种通过针对不同发育阶段的胚胎筛选环肽的mRNA展示文库来设计具有广泛渗透活性的膜渗透环肽（MPP）的方法。通过鉴定能够渗透果蝇（果蝇）胚胎和哺乳动物细胞的肽，证明了所提出的方法。所选肽环[ Glut -MRKRHASRRE- K *]对接受最低限度透化预处理的胚胎以及人胚胎干细胞和鼠成纤维细胞系表现出很强的渗透活性。值得注意的是，在胚胎和哺乳动物细胞中，环肽的表现均优于其线性对应物和对照 MPP。利用共聚焦显微镜和单细胞流式细胞术分析来定性和定量评估渗透程度。这些 MPP 在研究和无中断控制细胞内或胚胎内过程方面具有潜在的应用。