Development of tandem cation exchange chromatography for high purity extracellular vesicle isolation: The effect of ligand steric availability

Purification of extracellular vesicles for research and therapeutic applications requires updated methodology to address the limitations of traditional ultracentrifugation and other size-based separation techniques. Their downfalls include induced extracellular vesicle aggregation, low yields, poor scalability and one-dimensionality of the separation process, as the size or sedimentation speed of extracellular vesicles is often the only selection criterion. Ion exchange chromatography is a promising alternative or supplementary method candidate, as it offers a different approach for extracellular vesicle separation, which is surface charge. For now, mostly anion exchange chromatography has been evaluated for extracellular vesicle purification, as it successfully relies on the strongly negative surface charge of extracellular vesicles. However, as extracellular vesicles are very complex in their structure, also cation exchange chromatography could be applicable, due to individual cationic domains on the extracellular vesicle surface. Here, we compare anion exchange chromatography to different types of cation exchange chromatography for the purification of platelet extracellular vesicle samples also containing plasma-derived impurities. We found that the choice of resin structure used for cation exchange chromatography is critical for binding platelet extracellular vesicles, as a conventional-type cation exchanger was found to only capture and elute less than 20 % of extracellular vesicles. With the tentacle-type resin, it was possible to obtain comparable platelet extracellular vesicle yields (over 90 %) with cation exchange chromatography compared to anion exchange chromatography, as well as superior purity, especially when it was combined to conventional cation exchange resin.