Precision measurements of size, refractive index and concentration of nanoparticles in polydispersions
Background
Characterization of the size, material properties and concentration of particles in liquid suspensions is in high demand, for example, for the analysis of extracellular vesicles (EVs) in body fluids. However, existing methods are often limited in sensitivity and cannot handle a high degree of polydispersion.
Methods
We present interferometric nanoparticle tracking analysis (iNTA) [1], which combines nanoparticle tracking analysis (NTA) with interferometric scattering (iSCAT) microscopy to achieve higher sensitivity than traditional NTA instruments. We show that iNTA can measure the size and refractive index of individual nanoparticles with unprecedented precision. Furthermore, we demonstrate that the concentrations of different subpopulations in polydispersions can be determined from the trajectory numbers [2].
Results
We benchmarked iNTA with synthetic nanoparticles and showed that gold nanoparticles as small as 10 nm can be measured. Afterwards we show that iNTA can extract the size and internal structure of liposomes and EVs. In addition, we demonstrate that iNTA can differentiate EVs from lipoproteins in blood plasma-derived samples [3], which is not possible with conventional NTA. Finally, we show that iNTA can differentiate viruses from EVs in SARS-CoV2 infected cell supernatants.
Conclusion
We have shown that iNTA is a useful tool not only for characterization of particle size and refractive index, but also for quantitative assessment of particle concentration, even when sizes overlap. This is very useful for the quantification of EVs where co-isolates are often present in the samples.
Keywords
iNTA, nanoparticle size, nanoparticle refractive index, nanoparticle concentration, polydispersions
References
[1] A. Kashkanova, M. Blessing, A. Gemeinhardt, D. Soulat, and V. Sandoghdar. Precision size and refractive index analysis of weakly scattering nanoparticles in polydispersions. Nat. Methods, 19(5):586–593, 2022.
[2] A. Kashkanova, D. Albrecht, M. Küppers, M. Blessing, and V. Sandoghdar. Measuring concentration of nanoparticles in polydisperse mixtures using interferometric nanoparticle tracking analysis (iNTA). Accepted to ACS Nano, 2024.
[3] A. Kashkanova, M. Blessing, M. Reischke, J. Baur, A. Baur, V. Sandoghdar, and J. Van Deun. Label-free discrimination of extracellular vesicles from large lipoproteins. J. Extracell. Vesicles, 12(8), 2023.
Funding/Acknowledgments
Max Planck Society, Bundesministerium für Bildung und Forschung Alexander von Humboldt Foundation Christiane Nüsslein-Volhard Foundation
Authors
Anna Kashkanova1,3 and Vahid Sandoghdar1,2,3 (Corresponding Author: vahid.sandoghdar[at]mpl.mpg[dot]de)