Electrogenerated chemiluminescence biosensor for microRNA detection incorporating enzyme-free dual DNA cyclic amplification and Ru(bpy)32+-functionalized metal-organic framework

Herein, a novel electrogenerated chemiluminescence (ECL) biosensor for the determination of microRNA was developed on the basis of enzyme-free dual signal amplification and Ru(bpy) 3 2+ -functionalized metal-organic frameworks (Ru@MIL-101(Al)–NH 2 ) as ECL signal labels. MicroRNA-21 (miRNA-21) was used as a model target, which initiated the toehold-mediated strand displacement reaction (TSDR). The first cyclic amplification TSDR converted a small quantify of miRNA-21 to abundant report strands (RS), which then catalyzed the second cyclic amplification catalytic hairpin assembly (CHA). The CHA ran cyclically to produce numerous H1–H2 duplexes with the exposed segment. Finally, the newly exposed segment of H2 could bind with the ECL probe (DNA-Ru@MIL-101(Al)–NH 2 ), leading to an evident ECL signal enhancement. The results showed that the ECL intensity varied linearly with the logarithm of the concentration of miRNA-21 ranging from 0.01 to 10,000 pM. The detection limit was as low as 4 fM because of the signal amplification through TSDR and CHA processes coupling with Ru@MIL-101(Al)–NH 2 . In addition, this biosensor has been successfully applied to detect miRNA-21 in MCF-7 cells, providing great potential for the related clinical diagnosis. • Ru@MIL-101(Al)–NH 2 acts as the ECL signal labels. • The TSDR and CHA are collaborative to enhance ECL intensity. • The ECL biosensor can be applied to determine miRNA-21 in MCF-7 cells. • The strategy can be referred to develop biosensors for other miRNAs.