Quantitative Measurement of Extracellular Vesicle-Sized Particles in Blood Plasma by Laser Diffraction Without an...

Extracellular vesicles (EVs) circulate in blood and may serve as disease biomarkers. However, in atrial fibrillation (AF), reliable circulating biomarkers remain limited. Conventional quantification of EVs requires cumbersome extraction procedures that can reduce quantitative accuracy. We investigated whether laser diffraction (LD) enables accurate and reproducible measurement of EV-sized particles in blood plasma without an extraction process.

LD was used to measure particle size and concentration of synthetic liposomes and plasma-derived EV fractions, and the results were compared with nanoparticle tracking analysis (NTA). Particles in plasma were then measured by LD with and without an extraction process, and the impact of dietary conditions was evaluated. Finally, particle concentrations in fasting plasma were compared between 20 controls without AF and 20 patients with AF.

For both synthetic liposomes and extracted EV fraction, LD showed quantitative accuracy comparable to NTA, with higher reproducibility. LD-based measurement in plasma without an extraction process produced a size distribution profile similar to that obtained after extraction, whereas the peak particle concentration decreased after extraction, suggesting partial particle loss during processing. Postprandial samples showed contamination by chylomicrons and very-low-density lipoproteins, which shifted the size distribution toward larger particles and interfered with plasma measurement. Using fasting plasma, the concentration of EV-sized particles measured by LD was significantly higher in AF patients than in controls (p = 0.0225).

LD enables accurate and highly reproducible quantification of EV-sized particles in fasting plasma without an extraction process and may support proof-of-concept biomarker assessment in AF.