Split proximity circuit initiated CRISPR-Cas12a system profiling exosomal surface proteins for early cancer detection.

Early diagnosis of breast cancer is critical for improving prognosis, but traditional methods have limitations. Herein, we propose an SPC-CRISPR system for the sensitive and specific detection of multiple breast cancer exosomal proteins without prior exosome isolation. This system couples CRISPR system with an enzyme-free amplification method to achieve dual-signal amplification. SPC-CRISPR is based on a split proximity circuit (SPC) that triggers catalytic hairpin assembly (CHA), converting protein signals on the surface of exosomes into nucleic acid signals, and the CRISPR-Cas12a system enabling further signal amplification and output. The system targets phosphatidylserine (PS), MUC1, and EpCAM on exosomes: Tim4-modified magnetic beads capture PS-expressing exosomes, and dual-aptamers recognize MUC1 and EpCAM, enabling SPC assembly and subsequent amplification. In buffer and cell-derived exosomes, the SPC-CRISPR system showed a detection limit of 10 particles/μL (R = 0.990). Clinical tests utilizing merely 1 μL of serum samples successfully distinguished breast cancer patients from healthy donors (AUC = 0.9778, accuracy = 91.23 %), detected stage 0 breast cancer patients against healthy controls (accuracy = 92.59 %), and differentiated metastatic from non-metastatic cases (p < 0.001). The combination of high sensitivity, minimal sample requirements, and an exosome isolation-free workflow positions the SPC-CRISPR system as a promising tool for the clinical early detection and classification of breast cancer, with broader applicability to other cancers by swapping the corresponding aptamers.