A comparison of blood plasma exosome enrichment strategies for proteomic analysis.

Proteomic analysis of exosomes (EXs) poses a significant challenge. A ‘gold-standard’ method for plasma EX enrichment for downstream proteomic analysis is yet to be established. Methods were evaluated for their capacity to successfully isolate and enrich EXs from plasma, minimise the presence of highly abundant plasma proteins, and result in the optimum representation of exosomal (EXal) proteins by liquid chromatography tandem mass spectrometry. Plasma from four cattle (Bos taurus) of similar physical attributes and genetics were used. Three methods of EX enrichment were utilised: ultracentrifugation (UC), size-exclusion chromatography (SEC), and ultrafiltration (UF). These methods were combined to create four groups for methodological evaluation: UC+SEC, UC+SEC+UF, SEC+UC and SEC+UF. The UC+SEC method yielded the highest number of protein IDs.