Accurate and rapid quantification of PD-L1 positive exosomes by a triple-helix molecular probe.

Programmed death ligand-1 (PD-L1) positive exosomes (P-Exo) have been widely used for tumor diagnosis. However, accurate and rapid quantification of P-Exo remains challenging due to the heterogeneity of clinical individuals and isolation techniques. In this study, the triple-helix molecular probe (THMP) coupled with high-affinity silica-based TiO magnetic beads was used to isolate exosomes and to analyze the relative abundance of P-Exo in total exosomes (T-Exo). By employing this strategy, the entire analysis was completed within 70 min and the detection limit for P-Exo was 880 particles μL. Additionally, the relative abundance of P-Exo in T-Exo (RA) was calculated from their fluorescence ratio, which could avoid errors due to differences in samples and separation methods, and identify 1.5 × 10 P-Exo from 5 × 10 T-Exo per microliter. RA values were not only effective in distinguishing healthy volunteers from breast cancer patients, but also highly positively correlated with the stage of breast carcinoma. Overall, this strategy opens a new avenue for rapid and quantitative analysis of P-Exo, providing an opportunity for precise diagnosis and prediction of treatment efficacy in cancer.