Multivalent aptamer-linked tetrahedron DNA assisted catalytic hairpin assembly for accurate SERS assay of cancer-derived exosomes in clinical blood.

Exosome-based liquid biopsy plays an increasingly important role in non-invasive cancer diagnosis. However, due to their small size and low abundance, sensitive and accurate detection of cancer-derived exosomes in complex biological samples still faces great challenges. Herein, an ultrasensitive SERS assay based on the multivalent aptamer-linked tetrahedron DNA (MATD) assisted catalytic hairpin assembly (CHA) was developed for accurate detection of cancer-derived exosomes, including MATD-modified SERS sensing chip, identification SERS tags (IS), and assist SERS tags (AS). Taking SGC-7901 cell-derived exosomes as a test model, the exosomes can be captured onto the SERS sensing chip by the specific binding of multivalent aptamers to CD63 proteins, and then the MUC1 aptamers on the IS bind to the highly expressed MUC1 proteins on the SGC-7901 cell-derived exosomes to release the patch strands (P), further triggering the CHA-induced assembly of AuNP network structures between IS and AS with rich hotspots on SERS sensing chip. The proposed SERS assay can achieve ultra-high sensitivity low to 2.98 × 10 particles mL (i.e., approximately 6 exosome particles can be detected from 2 μL of biological sample) within 40 min, high specificity for identifying SGC-7901 cell-derived exosomes, and can accurately distinguish gastric cancer patients from healthy people, which shows the potential applications in clinical diagnosis.