Electrochemiluminescence biosensor for the thyroid cancer biomarker miRNA-146b-5p detection using Zr-based...

Cancer cell-derived exosomes serve as crucial biomarkers for thyroid cancer, which has emerged as the fourth most prevalent malignancy among urban Chinese women. However, achieving high sensitivity and precision in their in vitro detection remains challenging. Traditional diagnostic methods for thyroid cancer, including tumor-associated marker detection and imaging examinations, are limited by high costs and poor sensitivity. Among various biomarkers, miRNA-146b-5p has been identified as a key marker associated with the progression of thyroid cancer, which poses a formidable challenge in achieving exquisite sensitivity and precision in vitro detection. Herein, we developed an electrochemiluminescence (ECL) biosensor for the sensitive detection of the thyroid cancer marker miRNA-146b-5p, based on Zr-PTC and combining an ECL resonance energy transfer (ECL-RET) system with a toehold-mediated strand displacement reaction (TSDR) signal amplification strategy. Initially, Zr-PTC was employed as the ECL signal label, with miRNA-146b-5p as the model target to initiate the TSDR cycle, resulting in the release of the output chain (output). The output chain assisted the unfolding of hairpin DNA H1 (H1), which exposed its complementary sequence that hybridizes with the ECL quenching material (AgCl NPs-S1), thereby resulting in a significant reduction of the ECL signal. The combination of target cyclic amplification and metal-organic framework-based signal labeling significantly enhanced the sensitivity of the proposed biosensor, achieving limit of detection (LOD) for miRNA-146b-5p as low as 0.69 fM (S/N = 3). This innovative analytical methodology presents a promising strategy for detecting exosomal RNA biomarkers associated with thyroid malignancies. The integration of RET system with TSDR signal amplification not only enhanced detection sensitivity but also demonstrated robust reproducibility and stability, offering broad applicability for sensitive nucleic acid detection in human serum samples.