ZnO@CuS Nanoprobe-Assisted Electrochemical Biosensor Based on Multiple Cyclic Amplification for Highly Sensitive Detection of MicroRNA-155

The imbalanced expression of microRNA is related to many diseases and tumors, which can be used as a noninvasive biomarker to assist in the diagnosis, prognosis, and monitoring of cancer. A target conversion strategy-based electrochemical biosensor was developed by DNAzyme-cleavage dual cyclic signal amplification and the strand displacement reaction (SDR) to produce high electrochemical signals for microRNA-155 (miRNA-155) analysis. Thereinto, VSe₂/multi-walled carbon nanotubes (MWCNTs) with high conductivity were applied as the electrode surface material to provide more active sites and accelerate electron transportation. Then, the excellent immobilization efficiency and large specific surface area of the ZnO@CuS nanoprobes were applied as a recognition molecule carrier. Furthermore, hexaammineruthenium(III) chloride (RuHex), with superior electrochemical redox activity, acted as the electroactive indicator by intercalating into double-helix DNA through electrostatic interaction, which produced high current responses in the presence of the target. Therefore, this miRNA-155 biosensing platform exhibited a relatively low limit of detection of 0.11 fM, ranging from 0.5 fM to 5 nM, and demonstrated excellent repeatability and stability. Hence, this platform appeared to possess favorable human serum detection capacity and be suitable for early cancer diagnostics.