Spiropyran in Situ Switching: A Real-Time Fluorescence Strategy for Tracking DNA G‑Quadruplexes in Live Cells

DNA G-quadruplexes (G4s) in vivo have been linked to cancer and other diseases such as neurological disorders. Nondestructive fast detection of endogenous DNA G4s can provide specific real-time information, which is of particular interest for clinic accurate diagnosis. However, tools to probe live-cell endogenous DNA G4s in real time are very limited. Herein, we report the design and development of a fluorescent molecule QIN for the real-time detection of endogenous DNA G4s in live cells with the aid of a new spiropyran in situ switching (SIS) strategy. The lipophilic spiropyran-linked QIN differs from the other probes in that it can enter live cells readily within 15 s and can be in situ induced by DNA G4s to adopt its charged open form, causing a large red shift in the fluorescent emission wavelength. Live-cell super-resolution fluorescent imaging suggests that the SIS-based probe has high photostability and can be applied for the accurate detection of DNA G4s in complex biosystems with very high sensitivity and selectivity.体内的DNA G-四链体（G-quadruplexes，G4s）已被证实与癌症及神经系统疾病等多种疾病存在关联。对内源性DNA G4s进行无损快速检测，可获取特异性实时信息，这对于临床精准诊断具有重要意义。然而，能够实时探测活细胞内源性DNA G4s的工具仍十分有限。本研究报道了荧光分子QIN的设计与开发，借助全新的螺吡喃原位开关（spiropyran in situ switching，SIS）策略，实现活细胞内源性DNA G4s的实时检测。该携带有亲脂性螺吡喃基团的QIN探针与其他探针的不同之处在于，它可在15秒内快速进入活细胞，并能被DNA G4s原位诱导为带电开环构象，从而使荧光发射波长产生显著红移。活细胞超分辨率荧光成像结果表明，该基于SIS策略的探针具备优异的光稳定性，能够以极高的灵敏度和特异性，应用于复杂生物系统中DNA G4s的精准检测。