Colorimetric aptasensor for exosome detection in breast cancer liquid biopsy

Exosomes are nanoscale extracellular vesicles (EVs) that carry molecular signatures reflective of their cells of origin, making them attractive biomarkers for liquid biopsy applications. In this study, we present a rapid and highly specific colorimetric aptasensor for the detection of Gremlin-1 (GREM1)-expressing exosomes in serum. The sensing strategy relies on the disaggregation of gold nanoparticle (AuNP) clusters, initially formed by NaCl-induced aggregation, upon selective binding of the target. AuNPs were functionalized with a thiolated Ex.50.T aptamer specifically recognizing exosomal GREM1, and the binding event triggers a measurable spectral shift in the plasmonic profile. A detection limit below 106 exosomes/mL was achieved using serial dilutions of purified exosomes isolated from breast cancer serum samples, demonstrating the method’s sensitivity and robustness under controlled conditions. Applied to 100 clinical serum samples, the assay demonstrated excellent diagnostic performance, with 84% sensitivity and 90% specificity—values comparable to those of mammography—without requiring extensive sample processing. Comparative analysis with commercial ELISA and Ex.50.T aptamer-based ELONA confirmed the superior discriminatory power of the method proposed here. Transmission electron microscopy further corroborated the mechanism by revealing exosomes physically disrupting AuNP aggregates. These results highlight the diagnostic potential of exosome-focused sensing strategies and establish this aptamer-based colorimetric platform as a promising candidate for non-invasive screening of breast cancer through liquid biopsy.