Enrich for more exosomal proteins: Ascites and Urine

Isolate Exosomes and their Proteins from Ovarian Tumor Ascites Fluid

The quantity of protein was determined by the Bradford microassay method (Bio-Rad Laboratories), using BSA as a standard. Proteins from each exosome isolate were standardized to the original sample volume and equal volumes were applied per lane of a 12.5% SDS-PAGE gel. Western immunoblotting was performed to analyze the presence of the specific marker protein, placental alkaline phosphatase (PLAP). The SDS-PAGE gel was transferred to a nitrocellulose membrane, the membrane blocked for 1 hour at room temperature with non-fat dried milk, and probed overnight at 4°C with primary antibody. The bound immune complexes were visualized by enhanced chemiluminescence (ECL, Amersham Life Sciences) and quantitated by densitometry (Un-Scan-it Software, Silk Scientific Corp.).

Human urine samples (1 ml) were treated with 1 ml ExoQuick. Exosome pellets recovered were resuspended in 35µl PBS and the supernatants used as controls. Equal volumes (10µl) of urine supernatant (Sup) and exosome pellets (EXO) were separated on 4–15% gradient PAGE gels (Bio-Rad). Standard Western blot procedures with antibodies to Annexin V and Aquaporin-2 (both from Abcam, Inc.) were used to detect urine exosomal protein biomarkers.