Infected or malignant cells frequently secrete more exosomes, leading to elevated levels of disease-associated exosomes in the circulation. These exosomes have the potential to serve as biomarkers for disease diagnosis and to monitor disease progression and treatment response. However, most exosome analysis procedures require exosome isolation and purification steps, which are usually time-consuming and labor-intensive, and thus of limited utility in clinical settings. Researchers from the Arizona State University describe a rapid procedure to analyze specific biomarkers on the outer membrane of exosomes without requiring separate isolation and purification steps. In this method, exosomes are captured on the surface of a slide by exosome-specific antibodies and then hybridized with nanoparticle-conjugated antibody probes specific to a disease. After hybridization, the abundance of the target exosome population is determined by analyzing low-magnification dark-field microscope (LMDFM) images of the bound nanoparticles. This approach can be easily adopted for research and clinical use to analyze membrane-associated exosome biomarkers linked to disease.
Exosome quantification scheme
(A) Schematic of multi-well protein A/G slides (192 wells) used in this assay. (B) Target exosomes are directly captured from samples, including serum and plasma, by surface immobilization on the capture antibody (e.g. anti-EphA2 antibody) bound to the slide, and then incubated with gold nanorods conjugated with a detection antibody (e.g. anti-CD9 antibody) before analysis by DFM image analysis.