Abstract
Proteomic analysis of exosomes (EX) poses a significant challenge. A ‘gold-standard’ method for plasma EX enrichment for downstream proteomic analysis is yet to be established. Our group has performed a comprehensive study of multi-dimensional enrichment methods to determine their efficiency for protein isolation. Methods were evaluated for their capacity to a) successfully isolate and enrich EX from blood plasma, b) minimise the presence of highly abundant plasma proteins, and c) result in the optimum representation of EX proteins by liquid chromatography tandem mass spectrometry (LC-MS/MS). Blood plasma from four animals (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 enrichment methods were combined to create four groups for methodological evaluation: UC+SEC, UC+SEC+UF, SEC+UC and SEC+UF. UC+SEC yielded the highest number of protein IDs. Plasma protein identification was the least in SEC+UC, but this method yielded the lowest number of protein IDs overall. UC+SEC+UF decreased EX protein ID and did not improve purity compared to UC+SEC. Our data suggest that the method and sequence of EX enrichment strategy impacts protein ID, which may influence the outcome of biomarker discovery studies.
Novel protein identification methods for biomarker discovery via a proteomic analysis of periodontally healthy and diseased gingival crevicular fluid samples
