Multiplexed detection of bladder cancer microRNAs based on core-shell-shell magnetic quantum dot microbeads and cascade signal amplification

Bladder Cancer (BC) is the tenth most common cancer worldwide and the most malignant disease of the urinary system. The development of effective biomarkers and detection methods is of great significance for BC diagnosis and monitoring. This study demonstrated a microscopic imaging method for multiplexed detecting BC microRNAs (miRNAs) based on core-shell-shell bifunctional magnetic fluorescent beads (MFBs), with the integration of catalytic hairpin assembly (CHA) and terminal deoxynucleotidyl transferase (TdT)-mediated DNA polymerization. Assembled with quantum dots and magnetic nanoparticles, MFBs were utilized as the dual-functional carriers for optical encoding and magnetic separation. By introducing CHA-TdT cascade amplification, three encoded MFBs presented distinct changes of emissive-color, which could be decoded by the common fluorescence microscope. The strategy could reach femtomolar level for the detection of single miRNA, showing a wide linear dynamic range (6 logs). Point-mutation discrimination capability was also achieved for precise miRNA analyses. Moreover, this MFB-CHA-TdT strategy was capable of detecting BC-related miRNAs in clinical serum specimens, showing a great consistence with qRT-PCR. Overall, this work enabled multiplexed detection of miRNAs with ideal sensitivity, specificity and accuracy, which could be applied to the clinical detection and early diagnosis of BC.