Visual Detection of Multiplex microRNAs Using Cationic Conjugated Polymer Materials.

A simple, visual and specific method for simultaneous detection of multiplex microRNAs (miRNAs) has been developed by integrating duplex-specific nuclease (DSN)-induced amplification with cationic conjugated polymer (CCP) materials. The probe DNA with a complementary sequence to target miRNA is labeled with fluorescein dye (FAM). Without target miRNA, the single-strand DNA probe cannot be digested by DSN. Upon adding CCP, efficient fluorescence resonance energy transfer (FRET) from CCP to FAM occurs owing to strong electrostatic interactions between CCP and DNA probe. In the presence of target miRNA, the DNA probe hybridizes with target miRNA followed by digestion to small nucleotide fragments by DSN, meanwhile the miRNA is released and subsequently interacts again with probe, resulting in the cycled digestion of probe DNA. At this case, weak electrostatic interactions between oligonucleotide fragments and CCP lead to inefficient FRET from CCP to FAM. Thus by triggering the FRET signal from CCP to FAM, miRNA can be specially detected, and the fluorescence color change based on FRET can be visualized directly with naked-eyes under UV lamp. Furthermore, energy transfer cascade can be designed using CCP and DNA probes labeled at 5'-terminus with FAM and Cy3 dyes, and the multi-step FRET processes offer the ability to simultaneous detection of multiplex miRNAs.