A dual-signal lateral flow biosensing platform for visual detection of miRNA-21 in serum.

Herein, we report a rationally designed dual-mode lateral flow assay (LFA) biosensor for the visual detection of microRNA-21 (miRNA-21), a critical breast cancer biomarker. The platform utilizes a synergistic readout of colorimetric signals from gold nanoparticles (AuNPs) and fluorescent signals from quantum dot nanobeads (QDNBs). Upon the specific introduction of target miRNA-21, the conformation of optimized hairpin nucleic acid probes conjugated on the nanomaterials is disrupted. This structural transition exposes capture sites, generating an AuNP-mediated colorimetric signal and a restored QDNBs fluorescence signal on the test lines by mitigating the inner filter effect (IFE) between them. Compared with conventional single-signal or amplification-dependent miRNA sensors, the proposed LFA integrates amplification-free target recognition, complementary AuNP-based colorimetric and QDNB-based fluorescent readouts, and IFE-regulated fluorescence recovery on a single strip, enabling visual screening and smartphone-assisted semi-quantitative analysis without complex instrumentation. Under optimal conditions, both the colorimetric and fluorescent readouts display broad linear correlations with miRNA-21 concentrations (5-1000 nM and 2.5-1000 nM, respectively), the limits of detection (LOD) of 1.599 nM and 1.354 nM. Furthermore, the platform demonstrates remarkable specificity against homologous miRNAs and robust stability. In spiked human serum, the assay achieves satisfactory recovery rates (91.8%-113.2%) with relative standard deviations (RSDs) below 6.0%. Furthermore, a preliminary evaluation using serum samples from five breast cancer patients and five healthy individuals showed clearly distinguishable colorimetric and fluorescent responses between the two groups, supporting the effectiveness of the proposed probe for miRNA-21 detection in real serum samples. These results indicate the potential of the dual-signal LFA platform for further clinical application.