A highly sensitive colorimetric DNA sensor for MicroRNA-155 detection: leveraging the peroxidase-like activity of copper nanoparticles in a double amplification strategy

A novel and highly sensitive colorimetric DNA sensor for determination of miRNA-155 at attomolar levelsis presented that combines the peroxidase-like activity of copper nanoparticles (CuNPs) with the hybridization chain reaction (HCR) . The utilization of CuNPs offers advantages such as strong interaction with double-stranded DNA, excellent molecular recognition, and mimic catalytic activity. Herein, a capture probe DNA (P 1 ) was immobilized on carboxylated magnetic beads (MBs), allowing for amplified immobilization due to the 3D surface. Subsequently, the presence of the target microRNA-155 led to the formation of a sandwich structure (P 2 /microRNA-155/P 1 /MBs) when P 2 was introduced to the modified P 1 /MBs. The HCR reaction was then triggered by adding H 1 and H 2 to create a super sandwich (H 1 /H 2 ) n . Following this, Cu 2+ ions were attracted to the negatively charged phosphate groups of the (H 1 /H 2 ) n and reduced by ascorbic acid, resulting in the formation of CuNPs, which were embedded into the grooves of the (H 1 /H 2 ) n . The peroxidase-like activity of CuNPs catalyzed the oxidation reaction of 3,3',5,5'-Tetramethylbenzidine (TMB), resulting in a distinct blue color measured at 630 nm. Under optimal conditions, the colorimetric biosensor exhibited a linear response to microRNA–155 concentrations ranging from 80 to 500 aM, with a detection limit of 22 aM, and discriminate against other microRNAs. It was also successfully applied to the determination of microRNA–155 levels in spiked human serum. Graphical abstract