Anti-Fouling Magnetic Beads Combined with Signal Amplification Strategies for Ultra-Sensitive and Selective Electrochemiluminescence Detection of MicroRNAs in Complex Biological Media.

Herein, an electrochemiluminescence (ECL) microRNA biosensor based on anti-fouling magnetic beads (MBs) and two signal amplification strategies was developed. The newly designed anti-fouling dendritic peptide was wrapped on the surfaces of MBs to make them resistant to nonspecific adsorption of biomolecules in complex biological samples so as to realize accurate and selective target recognition. One of the amplification strategies was achieved through nucleic acid cycle amplification based on the DNAzyme on the surfaces of MBs. Then, the output DNA generated by the nucleic acid cycle amplification program stimulated the hybrid chain reaction (HCR) process on the modified electrode surface to generate the other amplification of the ECL response. Titanium dioxide nanoneedles (TiO2 NNs), as a co-reaction accelerator of the Ru(bpy)2(cpaphen)2+ and tripropylamine (TPrA) system, were wrapped with the electrodeposited polyaniline (PANI) on the electrode surface to enhance the ECL intensity of Ru(bpy)2(cpaphen)2+. The conducting polymer PANI can not only immobilize the TiO2 NNs but also improve the conductivity of the modified electrodes. The biosensor exhibited ultra-high sensitivity and excellent selectivity toward the detection of miRNA 21, with a detection limit of 0.13 fM. More importantly, with the anti-fouling MBs as a unique separation tool, this ECL biosensor was capable of assaying targets in complex biological media such as serum and cell lysate.