Ultrasensitive Fluorescence Monitoring and <i>in Vivo</i> Live Imaging of Circulating Tumor Cell-Derived miRNAs Using Molecular Beacon System

Circulating tumor cells (CTCs) have considerable clinical significance in cancer progression and prognosis. In this context, CTC-derived microRNAs (miRs) in blood and tissues have been proposed as the novel noninvasive biomarkers for monitoring tumor progression, especially at the early stages. To monitor circulating miRs, a tool should have high sensitivity, be a simple procedure, and allow detection in very small volumes. Thus, we designed a sensing tool for sensitive monitoring of blood or tissue miRs using a fluorophore-quencher probe-based molecular beacon (MB). This MB-based tool displayed an ultrasensitive limit of detection (LOD) level of 6.7 × 10–17 M and 8.7 × 10–17 for metastasis-derived miR-21a and miR-221, respectively. It also can discriminate miR-21a/221 from both guide strand miRs and its precursor forms (pre-miR). Furthermore, the tool discriminated between blood and tissue-related miR-21a/221-expression and detected metastasis and epithelial-mesenchymal transition and also describe a noninvasive miR fluorescence imaging of CTCs in a mouse model, showing the potential for clinical diagnosis and prognosis