SDR-assisted multi-primers triggering functional signal hairpin probe for miRNA detection with enzyme-free and high sensitivity

MiRNA can exist in body fluids and its changes directly affect human life and health, which has been a research hotspot in recent years. In this work, we designed an enzyme-free sensing system for highly sensitive detection of miRNA-21 based on strand displacement reaction (SDR) that can recycle the target and functional hairpin probes (HP) that modified on upconversion nanomaterials (UCNPs). The target gene circulates through the SDR process and completes the initial signal amplification process. Then, the C2 sequences and targets released by the SDR process can continue to be combined with functional hairpin probes modified with fluorophore and quenching groups. After infrared irradiation, HP is broken, and C2 or the target can take the fluorophores away from the quenching group, so that the fluorescence signal can be detected to achieve highly sensitive detection of the target. In sensing system, the use of magnetic beads can reduce the background signal during the reaction process, and the functional hairpin probe can accurately turn the signal on and off. The sensor system not only shows excellent detection performance (detection limit of 30.3 fM) in buffer and actual detection, but also has excellent selectivity, which can provide a new detection method for miRNA-21 detection.