Conformational change-based electrochemical biosensor for the simple and highly selective detection of miRNA in whole serum

Abstract

MicroRNAs (miRNAs) have emerged as powerful biomarkers for early-stage disease detection and prognosis support. However, their reliable quantification in complex biological fluids remains a significant challenge. Here, we present a simple and robust electrochemical DNA (E-DNA) sensor for the direct detection of miRNA-29c in whole human serum. The sensing mechanism harnesses the conformational change that occurs upon miRNA hybridization to the immobilized DNA capture probe. By exploiting the intrinsic base-pairing specificity of nucleic acids, our system achieves high selectivity, while the conformational change-based sensing mechanism confers resistance to electrode fouling. This dual advantage enables sensitive miRNA detection in complex media and effective discrimination of closely related miRNA sequences. Under optimized conditions, the biosensor exhibited a sigmoidal response to miRNA-29c in whole serum across the concentration range of 0.1–100 nM and showed excellent agreement with the Langmuir–Hill model (R² = 0.994). Notably, the sensor demonstrated outstanding recovery rates (±10%) when challenged with serum spiked with known miRNA-29c concentrations. Furthermore, it displayed high selectivity and specificity in serum, showing significantly lower responses to non-complementary and two-base-mismatched sequences. Overall, the platform enables reagentless, amplification-free, and direct detection of miRNA in complex matrices such as whole serum, while maintaining high accuracy, reproducibility, and resistance to fouling. These findings underscore the efficacy of the conformational change-based electrochemical sensing approach, offering a promising avenue for practical, point-of-care miRNA diagnostics in clinically relevant settings.