Enzyme-free nucleic acid and luminescent material cascade amplifications enable urinary dual miRNAs assay for non-invasive bladder cancer diagnosis

We presented a facile biosensing strategy for the detection of dual microRNAs (miRNA-21 and miRNA-126) in urine samples from bladder cancer (BC) patients. The fluorescent homogeneous detection of miRNAs was achieved by elaborate parallel catalytic hairpin assembly (CHA) integrated with material cascade amplifications. The continuous release of G-quadruplex (G4) sequences and Hg2+ was attributed to the specific recognition between the miRNAs and the corresponding hairpin oligonucleotides. Assisted by the streptavidin-(T-Hg2+-T-biotin)4 structures, more Hg2+ emission was obtained, and the spatial site block effect was used to order its distribution, significantly improving the selective recognition performance of cadmium telluride quantum dots (CdTe QDs) (1.4–2.9 times). Furthermore, the peroxidase-like activity of G4-hemin was used to catalyze the oxidation of dopamine (DA) to fluorescence-enhanced polydopamine (PDA). The generated PDA signal and the Hg2+-quenched CdTe QDs signal completed the synchronous detection to achieve a high-sensitivity analysis of the dual miRNAs. The limit of detection (LOD) of both miRNAs was as low as the fM level. Eventually, 56 clinical urine samples were quantified. The results showed satisfying specificity (100%) and sensitivity (92%) with a strong clinical agreement, including computed tomography (CT) and pathology findings, indicating a rapid non-invasive solution for early diagnosis of BC.