High-Sensitivity\nHomogeneous Detection of miRNA-155\nGoverned by DNA Walker-Regulated Surface DNA Density of Magnetic Electrochemiluminescence\nNanoparticles

Homogeneous electrochemiluminescence (ECL) has gained\nattention\nfor its simplicity and stability. However, false positives due to\nsolution background interference pose a challenge. To address this,\nmagnetic ECL nanoparticles (Fe<sub>3</sub>O<sub>4</sub>@Ru@SiO<sub>2</sub> NPs) were synthesized, offering easy modification, magnetic\nseparation, and stable luminescence. These were utilized in an ECL\nsensor for miRNA-155 (miR-155) detection, with locked DNAzyme and\nsubstrate chain (mDNA) modified on their surface. The poor conductivity\nof long-chain DNA significantly impacts the conductivity and electron\ntransfer capability of Fe<sub>3</sub>O<sub>4</sub>@Ru@SiO<sub>2</sub> NPs, resulting in weaker ECL signals. Upon target presence, unlocked\nDNAzyme catalyzes mDNA cleavage, leading to shortened DNA chains and\nreduced density. In contrast, the presence of short-chain DNA has\nminimal impact on the conductivity and electron transfer capability\nof Fe<sub>3</sub>O<sub>4</sub>@Ru@SiO<sub>2</sub> NPs. Simultaneously,\nthe material surface’s electronegativity decreases, weakening\nthe electrostatic repulsion with the negatively charged electrode,\nresulting in the system detecting stronger ECL signals. This sensor\nenables homogeneous ECL detection while mitigating solution background\ninterference through magnetic separation. Within a range of 100 fM\nto 10 nM, the sensor exhibits a linear relationship between ECL intensity\nand target concentration, with a 26.91 fM detection limit. It demonstrates\nhigh accuracy in clinical sample detection, holding significant potential\nfor clinical diagnostics. Future integration with innovative detection\nstrategies may further enhance sensitivity and specificity in biosensing\napplications.