Biomimetic machines that can convert mechanical actuation to adaptive coloration in a manner analogous to cephalopods have found widespread applications at various length scales. At the nanoscale, a transmutable nanomachine with adaptive colors that can sense and mediate cellular or intracellular interactions is highly desirable. Here, we report the design of a DNA framework nanomachine (DFN) that can autonomously change shape in response to pH variations in single synaptic vesicles, which, in turn, displays adaptive fluorescent colors with a mechano-fluorescence actuation mechanism. To construct a DFN, we used a tetrahedral DNA nanostructure as the framework to incorporate an embedded pH-responsive, i-motif sequence tagged with a Förster resonance energy transfer pair and an affinity cholesterol moiety targeting vesicular membranes. We found that endocytosed DFNs are individually trapped in single endocytic vesicles in living synaptic cells due to the size-exclusion effect. The adaptive fluorescence coloration of DFNs enabled single-vesicle quantification of resting pH values in a processive manner, allowing long-term tracking of the exocytosis and fusion dynamics in intracellular processes and cell-cell communications.

中文翻译：

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用 DNA 框架纳米机器在单个突触小泡中进行机械荧光驱动

可以以类似于头足类动物的方式将机械驱动转换为自适应着色的仿生机器已在各种长度尺度上得到广泛应用。在纳米尺度上，非常需要一种具有自适应颜色的可变形纳米机器，它可以感知和调节细胞或细胞内的相互作用。在这里，我们报告了一种 DNA 框架纳米机器 (DFN) 的设计，它可以根据单个突触小泡的 pH 值变化自主改变形状，进而通过机械荧光驱动机制显示自适应荧光颜色。为了构建 DFN，我们使用四面体 DNA 纳米结构作为框架，将嵌入的 pH 响应 i-motif 序列与 Förster 共振能量转移对和靶向囊泡膜的亲和胆固醇部分标记在一起。我们发现，由于尺寸排阻效应，被内吞的 DFN 被单独困在活突触细胞的单个内吞小泡中。DFN 的适应性荧光显色能够以连续的方式对静息 pH 值进行单囊泡定量，从而可以长期跟踪细胞内过程和细胞间通讯中的胞吐作用和融合动力学。