Salivary Extracellular Vesicles Separation: Analysis of Ultracentrifugation-Based Protocols

Abstract

Introduction: The clinical potential of extracellular vesicles (EVs) is widely acknowledged, yet the standardization and reproducibility of its separation remain challenging. This study compares three protocols: ultracentrifugation (UC), UC with purification step (UC + PS), and a combined protocol using polymer-based precipitation and UC (PBP + UC). Methods: Salivary samples were collected from healthy donors. EVs were separated (UC, UC + PS, and PBP + UC) and characterized using transmission electron microscopy, nanoparticle tracking analysis, EV purity, RNA concentration, and Western blotting. miRNA expression was evaluated by quantitative RT-PCR. Statistical analyses comparing groups were performed using ANOVA. Results: All methods successfully separated CD9+ and CD63+ EVs from saliva. The UC + PS and PBP + UC protocols yielded the highest concentrations of EVs, enriched in < 200 nm vesicles. EV purity and RNA recovery were comparable among all methods. Expression of miR-16, miR-27a, and miR-99a was successfully detected using all methods. Conclusions: The UC + PS and PBP + UC protocols demonstrate comparable efficiency in separating salivary EVs. However, the combined PBP + UC protocol, with its simplified processing capability, offers a significant advantage, particularly in the initial phase of EV separation. This finding suggests its potential application in clinical settings where time-sensitive simple processing is critical. Further validation is needed to confirm its effectiveness for transcriptomic and proteomic analyses.