State Key Laboratory of Chemo/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering , Hunan University , Changsha 410082 , P. R. China.
Anal Chem. 2019 Aug 20;91(16):10366-10370. doi: 10.1021/acs.analchem.9b02514. Epub 2019 Jul 29.
DNA nanomachines have received great interest due to their potential to mimic various natural biomolecular machines. Intracellular pH sensing and imaging are of great significance to understand cellular behaviors and disease diagnostics. In this work, we report the novel molecular switching of a self-assembled 3D DNA triangular prism nanomachine (TPN) for pH sensing and imaging in living cells. The TPN was self-assembled in quantitative yields by hybridization with two DNA triangles and three I-strands (containing i-motif sequences). At acidic conditions, the TPN was compressed due to the I-strand that formed an intramolecular i-tetraplex, which was in between the fluorophores Cy3 and Cy5, resulting in a significant fluorescence resonance energy transfer (FRET) signal. At neutral or weakly alkaline conditions, the TPN adopted an extended state due to the random coil form of the I-strand, leading to spatial separation of the two fluorophores and the FRET being blocked. The TPN was fully reversible and could rapidly respond to the pH changes, entered into living cells automatically via an endocytic pathway, monitored spatiotemporal pH changes during endocytosis, maintained its structural integrity after escape from lysosomes, still had the ability for pH sensing, and also visualized pH fluctuations under varying stimuli in living cells. We foresee that this TPN can become a generic platform for a pH-related cell biology study and in disease diagnostics.
DNA 纳米机器因其能够模拟各种天然生物分子机器而受到广泛关注。细胞内 pH 值的感应和成像对于理解细胞行为和疾病诊断具有重要意义。在这项工作中，我们报告了一种自组装的 3D DNA 三角棱柱纳米机器（TPN）的新型分子开关，用于活细胞中的 pH 值感应和成像。TPN 通过与两条 DNA 三角形和三条 I 链（包含 i-motif 序列）杂交以定量产率自组装。在酸性条件下，由于 I 链形成了分子内 i-四聚体，位于荧光团 Cy3 和 Cy5 之间，TPN 被压缩，导致显著的荧光共振能量转移（FRET）信号。在中性或弱碱性条件下，由于 I 链呈随机卷曲形式，TPN 呈伸展状态，导致两个荧光团的空间分离，FRET 被阻断。TPN 是完全可逆的，可以快速响应 pH 值的变化，通过内吞途径自动进入活细胞，监测内吞过程中的时空 pH 值变化，从溶酶体中逃逸后仍保持结构完整性，仍然具有 pH 值感应能力，并在活细胞中可视化不同刺激下的 pH 值波动。我们预计，这种 TPN 可以成为用于 pH 相关细胞生物学研究和疾病诊断的通用平台。
