Rolling circle amplification assisted dual signal amplification colorimetric biosensor for ultrasensitive detection of leukemia-derived exosomes.

Tumor-derived exosomes as a liquid biopsy marker hold great promising for the accurate tumor diagnosis. However, the visual exosomes detection method with high sensitivity and convenience is still a challenge and highly valuable in the clinical application. Herein, we fabricated a colorimetric biosensor that could visually detect leukemia-derived exosomes, and dual amplified the signal based on the rolling circle amplification (RCA) assisted platform. To avoid the interference of components in serum, trigger-aptamer complex was firstly modified on the magnetic beads (MBs) to recognize exosomes, and then release trigger probe to initiate RCA reaction. Therefore, the trigger probe could produce long repeated sequences and hybridized with numerous signal probe. After that, GNPs-HRP (HRP modified gold nanoparticles) bound with signal probe and induced dramatic color change of TMB to achieve the sensing of exosomes. Benefiting from the RCA assisted dual signal amplification, the presented method showed a limit of detection as low as 100 particles/μL. Moreover, this method exhibited good specificity to distinguish healthy and leukemia patients, suggesting its great potential for clinical diagnosis.