Magnetic-enhanced fluorescence sensing of tumor miRNA by combination of MNPs@PDA with duplex specific nuclease.

Highly sensitive and specific detection of miRNA still remains challenging. In this work, a simple and sensitive fluorescence biosensor has been developed for detection of miRNA by combining the magnetic nanoparticles coated with poly-dopamine (MNPs@PDA) with duplex specific nuclease (DSN). The MNPs@PDA could be easily synthesized via autoxidation of dopamine on the surface of magnetic nanoparticles. The MNPs@PDA could specifically bind with the FAM-labeled single-strand DNA (ssDNA) probes via polyvalent metal-mediated coordination, resulting in the quench of fluorescence signal. The MNPs@PDA exhibited good anti-interference performance in complex matrix. The inner filter effect (IFE) of the MNPs@PDA could be eliminated via magnetic separation. In the presence of specific miRNA, DSN digested the DNA in the DNA-miRNA duplexes and small fragments were formed. The force between these small fragments and MNPs@PDA was negligible, resulting in the occurrence of fluorescence signal. Due to the incorporation of DSN, signal amplification was realized via the recycling process. The established method achieved a low detection limit down to 0.42 pM. The linear concentration range was from 5 pM to 5 nM. Moreover, this method also had high specificity. Remarkably, the target miRNAs extracted from human cells were detected by using the sensing platform.