Dual-Wavelength Surface Plasmon Resonance for Determining the Size and Concentration of Sub-Populations of Extracellular Vesicles

Publication year: 2016
Authors: Rupert D.L.M. 1, Shelke G.V. 2, Emilsson G. 1, Claudio V. 1, Block S. 1, Lässer C. 2, Dahlin A. 1, Lötvall J.O. 2, Bally M. 1,3, Zhdanov V.P. 1,4, Höök F. 1
Affiliations:
1 - Department of Physics, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden
2 - Krefting Research Centre, Department of Internal Medicine and Clinical Nutrition, University of Gothenburg, SE-405 30 Gothenburg, Sweden
3 - Institut Curie, Centre de Recherche, CNRS, UMR 168, Physico-Chimie Curie, F-75248 Paris, France
4 - Boreskov Institute of Catalysis, Russian Academy of Sciences, 630090 Novosibirsk, Russia
Published in: Analytical Chemistry, 2016, Vol. 88 (20), p. 9980–9988
doi: 10.1021/acs.analchem.6b01860

Accurate concentration determination of subpopulations of extracellular vesicles (EVs), such as exosomes, is of importance both in the context of understanding their fundamental biological role and of potentially using them as disease biomarkers. In principle, this can be achieved by measuring the rate of diffusion-limited mass uptake to a sensor surface modified with a receptor designed to only bind the subpopulation of interest. However, a significant error is introduced if the targeted EV subpopulation has a size, and thus hydrodynamic diffusion coefficient, that differs from the mean size and diffusion coefficient of the whole EV population and/or if the EVs become deformed upon binding to the surface. We here demonstrate a new approach to determine the mean size (or effective film thickness) of bound nanoparticles, in general, and EV subpopulation carrying a marker of interest, in particular. The method is based on operating surface plasmon resonance simultaneously at two wavelengths with different sensing depths and using the ratio of the corresponding responses to extract the particle size on the surface. By estimating in this way the degree of deformation of adsorbed EVs, we markedly improved their bulk concentration determination and showed that EVs carrying the exosomal marker CD63 correspond to not more than around 10% of the EV sample.


MP-SPR keywords: biotinylated liposomes, concentration, extracellular vesicles, film thickness, size