Identification and Detection Application of Specific Aptamer for Metastatic Colorectal Cancer Exosomes

Liquid biopsy-based exosome analysis offers significant potential for early cancer diagnosis. As key targets in liquid biopsies, exosomes carry surface proteins that can serve as tumor-specific biomarkers, enabling a non-invasive and dynamically approach for early tumor detection. Metastatic colorectal cancer, one of the most lethal malignancies worldwide, accounts for a substantial proportion of cancer-related deaths. In this study, aptamer Q2 that screened through a streamlined exosome-systematic evolution of ligands by exponential enrichment (Exo-SELEX) screening process in previous work was studied to characterize its binding affinity for exosomes derived from metastatic colorectal cancer (CRC). Aptamer Q2 exhibited high affinity and specificity toward these exosomes, along with robust biological stability. Enzyme treatment assays indicated that the target of aptamer Q2 was a membrane protein located on the exosomal surface. In addition, leveraging the specific recognition capability of aptamer Q2 for metastatic colorectal cancer-derived exosomes, a quantitative exosome detection platform based on this aptamer was developed. The system enabled sensitive detection of plasma exosomes from clinical CRC patients, achieving a detection limit of 6.8× 105 particles/μL. This approach offered a new strategy for early diagnosis and monitoring of tumors.