MicroRNAs play a crucial role in regulating gene expression and cellular function. Reliable detection of miRNA is highly demanded in clinical diagnosis and therapy. Herein, we designed a structure-convertible DNA switch and constructed a novel switch-conversional ratiometric fluorescence biosensor (SCRF biosensor) for highly sensitive miRNA detection by the use of amplicon fragments to convert the structure of the switch. The DNA switch was a sophisticated designed single-strand DNA with a stem-loop structure and modified with two fluorophores (Cy3 and Cy5) and one quencher at specific sites of the switch. Amplicon fragments (c*) were produced by an exponential amplification reaction. When the c* hybridized to the loop of a DNA switch, the structure of the switch would convert, and fluorescence resonance energy transfer occurred between Cy5 and Cy3. Then two fluorescence signals with different trends would be observed. As a result, by the ratio of the two signals, we can quantitatively and quickly detect the target miRNA with the concentration range from 100 fM to 100 nM and the excellent detection limit down to 70.9 fM, providing this new SCRF biosensor broad application prospects.

中文翻译：

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开关转换比例荧光生物传感器用于miRNA检测。

MicroRNA在调节基因表达和细胞功能中起关键作用。临床诊断和治疗中对可靠检测miRNA的要求很高。在本文中，我们设计了一种结构可转换的DNA开关，并构建了一种新型的开关转换比例荧光生物传感器（SCRF生物传感器），该传感器通过使用扩增子片段来转换开关的结构来检测高灵敏度的miRNA。DNA开关是设计复杂的单链DNA，具有茎环结构，并在开关的特定位点用两个荧光团（Cy3和Cy5）和一个淬灭剂修饰。通过指数扩增反应产生扩增子片段（c *）。当c *与DNA开关的环杂交时，开关的结构会转换，Cy5和Cy3之间发生了荧光共振能量转移。然后将观察到具有不同趋势的两个荧光信号。结果，通过两种信号的比率，我们可以定量快速检测目标miRNA，其浓度范围从100 fM到100 nM，出色的检测限降至70.9 fM，为这种新型SCRF生物传感器提供了广阔的应用前景。