Quantitative proteomic analysis for evaluating affinity isolation of extracellular vesicles

Absolute quantification with mass spectrometry and isotope labeled internal standards has found broad applications in biomedical research. In the present research, it was used for developing and evaluating a new affinity based approach to isolate extracellular vesicles (EVs) from human plasma. First, a phage display peptide library was screened against EVs as a bait and absolute quantification of multiple proteins helped to select the best bait available. Then, absolute quantification was used to evaluate the efficiency of affinity chromatography on peptide-Sepharose. In summary, we have demonstrated that peptides with affinity to EVs selected from phage library screening can be valuable ligands for EVs isolation. Significance: Extracellular vesicles (EVs) have an important role in intercellular communication for all cell types. This makes EVs a promising new type of therapeutics capable to deliver drugs to specific sites with no off-target side effects. However, their isolation, and correct assignment of their biological function and properties remains an obscure field of research. In this study, we proposed to use MRM quantitation of a pattern of EVs and non-EVs proteins to develop a purification protocol based on affinity peptides selected from phage library screening. MRM quantification of EVs proteins can also help in identifying those that are subpopulation specific markers for further target-specific isolation.