Electrochemical biosensing of miRNA-155 based on nucleic acid recognition-induced multiple DNA release and Exo III-assisted target recycling

Here presents a sensing strategy for the detection of miRNA-155 based on a multi-amplification strategy, which involves nucleic acid recognition-induced multiple DNA release and Exonuclease III (Exo III)-assisted target recycling. Initially, cDNA-magnetic bead bioconjugates were employed to capture the target miRNA, triggering the release of two methylene blue (MB)-modified messenger DNAs (mDNAs). This step effectively doubles the amount of mDNAs-MB released, contributing to initial signal amplification. Subsequently, the target miRNA is recycled via Exo III-mediated cleavage, leading to the release of additional mDNAs-MB and further enhancing the signal. Finally, each capture probe (P1) is designed to hybridize with two mDNAs-MB, enabling dual signal recognition. As a result, the square wave voltammetry (SWV) measurements detected a significantly amplified MB peak current. The overall detection strategy integrates three synergistic amplification approaches: the release of multiple mDNAs, Exo III-assisted target miRNA recycling, and dual hybridization of mDNAs to P1. The miRNA-155, a recognized biomarker for breast cancer diagnosis, was used as the target to evaluate the biosensor's performance. The proposed electrochemical biosensor demonstrated a broad detection range from 0.1 pM to 1 mM and achieved a low detection limit of 0.026 pM, confirming its high sensitivity and potential applicability in cancer diagnostics.