Simultaneous Electrochemical Detection of miR-21 and miR-155 Breast Cancer Biomarkers Using a Dual-Signal Aptasensor Based on Cu/Cd Redox Probes.

Early and reliable detection of breast cancer-related microRNAs play a critical role in molecular diagnostics and personalized treatment strategies. In this work, a highly sensitive dual-channel electrochemical biosensor was developed for the simultaneous and independent detection of microRNA-21 and microRNA-155. The sensing interface was fabricated on an indium tin oxide electrode modified with a multilayer structure consisting of glutaraldehyde, polyaniline, and silver nanoparticles. Copper and cadmium metallic nanoparticles were employed as distinguishable electrochemical labels, enabling the generation of two well-separated redox signals using differential pulse voltammetry. Changes in peak current intensity were used as the analytical signal to evaluate sensor performance and optimize experimental parameters, including probe concentration, immobilization time, hybridization temperature, and electrolyte pH. Under optimized conditions, the biosensor exhibited a wide linear response range from 1.0 × 10-16 to 1.0 × 10-9 M, with ultralow limits of detection of 62.0 aM for microRNA-21 and 650.0 aM for microRNA-155. The platform demonstrated excellent selectivity, good repeatability and reproducibility, and stable performance for up to 3 weeks. Successful validation in human plasma samples with recovery values between 92% and 119% confirmed the reliability of the proposed system. Overall, this dual-channel biosensor provides a robust and ultrasensitive platform for multiplexed microRNA detection and shows strong potential for early stage breast cancer diagnostics.