The in situ precise quantification and simultaneous imaging of low abundance microRNAs (miRNAs) within living cells is critical for cancer diagnosis, yet it remains a significant challenge. Leveraging the excellent sensitivity and spatiotemporal resolution of dark-field microscopy (DFM) and fluorescence imaging, we have successfully devised a novel detection approach using dual-signal reporter probes (DSRPs). These probes allow for highly sensitive detection of miRNA-21 in living cells via toehold-mediated strand displacement cascades. The DSRPs were constructed by Au nanoparticles and Ag nanoclusters core-satellite nanostructures. After the recognition of miRNA-21, the strand displacement cascades were triggered, inducing the disassembly of the Au/Ag core-satellite nanostructure with apparent scattering intensity decrease and peak wavelength shifts. Additionally, the fluorescence of Ag clusters could be recovered and further enhanced when in close proximity to specific guanine-rich strands. The dual-signal response capability enables the accurate detection of miRNA-21 from 1 fM to 1 nM, with a limit of detection reached 0.75 fM. DFM and fluorescent imaging of living cells efficiently confirms the applicable detection of miRNA-21 in complex detection media. The biosensor based on DSRPs represents a promising nanoplatform for visual monitoring and imaging of biomolecules in living cells, even at the single particle level.

中文翻译：

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利用核心卫星等离子体纳米探针对活细胞中的 microRNA-21 进行暗场成像和荧光双模式检测

活细胞内低丰度 microRNA (miRNA) 的原位精确定量和同步成像对于癌症诊断至关重要，但这仍然是一个重大挑战。利用暗视野显微镜 (DFM) 和荧光成像的出色灵敏度和时空分辨率，我们成功设计了一种使用双信号报告探针 (DSRP) 的新型检测方法。这些探针可通过立足点介导的链置换级联对活细胞中的 miRNA-21 进行高度灵敏的检测。 DSRP 由金纳米颗粒和银纳米团簇核-卫星纳米结构构成。识别 miRNA-21 后，链位移级联被触发，导致 Au/Ag 核心卫星纳米结构解体，散射强度明显降低，峰值波长发生变化。此外，当靠近特定的富含鸟嘌呤的链时，银簇的荧光可以恢复并进一步增强。双信号响应能力能够准确检测1 fM至1 nM的miRNA-21，检测限达到0.75 fM。活细胞的 DFM 和荧光成像有效地证实了 miRNA-21 在复杂检测介质中的适用检测。基于 DSRP 的生物传感器代表了一种有前途的纳米平台，用于活细胞中生物分子的视觉监测和成像，甚至在单颗粒水平上也是如此。