Size and refractive index determination of extracellular vesicles smaller than 70 nm in a nano-fluidic optical fiber
||E. van der Pol, F.A. Coumans, S. Weidlich, Y. Lahini, M.A. Schmidt, T.G. van Leeuwen, A. Sturk, R. Nieuwland, and S. Faez|
||International Society for Extracellular Vesicles 2016, Rotterdam, The Netherlands|
||May 6, 2016|
Introduction: State-of-the-art detection methods show that typically ~70% of the extracellular vesicles (EV) have a diameter <70 nm. Thus far, EV <70 nm have only been studied in frozen state or with methods requiring EV to be adhered to a surface. Thus, the majority of EV have never been studied in their physiological environment. Here we present a novel label-free optical method to track single EV <70 nm in suspension. We use the method to determine the diameter and refractive index (RI) of EV.
Methods: EV from human cell-free urine (
Results: Using a nano-fluidic optical fiber, we could track single EV as small as 50 nm for >60 seconds by elastic light scattering. Furthermore, by combining data on thermal diffusion and light scattering, we confirmed that most EV have an RI <1.4.
Summary/conclusion: For the first time, we have tracked single EV <70 nm freely diffusing in suspension to determine their diameter and RI. Knowledge on the diameter and RI of EV is essential to data interpretation and standardization. Potential applications of the nano-fluidic optical fiber are dimensional characterization, zeta potential analyses and particle-particle interaction analyses of the smallest EV present.