Recent advances in optical label-free characterization of extracellular vesicles

Abstract

Extracellular vesicles (EVs) are complex biological nanoparticles endogenously secreted by all eukaryotic cells. EVs carry a specific molecular cargo of proteins, lipids, and nucleic acids derived from cells of origin and play a significant role in the physiology and pathology of cells, organs, and organisms. Upon release, they may be found in different body fluids that can be easily accessed via noninvasive methodologies. Due to the unique information encoded in their molecular cargo, they may reflect the state of the parent cell and therefore EVs are recognized as a rich source of biomarkers for early diagnostics involving liquid biopsy. However, body fluids contain a mixture of EVs released by different types of healthy and diseased cells, making the detection of the EVs of interest very challenging. Recent research efforts have been focused on the detection and characterization of diagnostically relevant subpopulations of EVs, with emphasis on label-free methods that simplify sample preparation and are free of interfering signals. Therefore, in this paper, we review the recent progress of the label-free optical methods employed for the detection, counting, and morphological and chemical characterization of EVs. We will first briefly discuss the biology and functions of EVs, and then introduce different optical label-free techniques for rapid, precise, and nondestructive characterization of EVs such as nanoparticle tracking analysis, dynamic light scattering, atomic force microscopy, surface plasmon resonance spectroscopy, Raman spectroscopy, and SERS spectroscopy. In the end, we will discuss their applications in the detection of neurodegenerative diseases and cancer and provide an outlook on the future impact and challenges of these technologies to the field of liquid biopsy via EVs.

Extracellular vesicles and their cells of origin: Open issues in autoimmune diseases

“…Isolation ( 93 ), characterization ( 94 ), labeling, and quantification strategies of different EV subtypes are constantly evolving ( 95 ). It should be noted that the various isolation methods of EVs end with different characteristics and potencies in terms of application ( 96 , 97 ).…”

Toward the nanoscale chemical and physical probing of milk-derived extracellular vesicles using Raman and tip-enhanced Raman spectroscopy

“…4,5 As a consequence of the increasing interest in EVs, a variety of analytical techniques have been employed to extensively study them, in order to gain a comprehensive overview of their morphology, functionality, and chemical composition. 6,7 Raman spectroscopy is a nondestructive technique which can provide a unique fingerprint of the chemical composition of a sample through the analysis of molecular vibrational modes. The Raman spectrum is obtained when the sample is irradiated with a monochromatic laser and contains all the characteristic peaks corresponding to the vibrational frequencies of the molecules present on the sample.…”

Practical tips and new trends in electrochemical biosensing of cancer-related extracellular vesicles

“…In the last decade, multiple techniques have been used to detect and/or characterise EVs, including western blotting, mass spectrometry, flow cytometry, nanoparticles tracking analysis, dynamic light scattering, tunable resistive pulse sensing, transmission electron microscopy, atomic force microscopy, and enzyme-linked immunosorbent assays [ 10 – 13 ]. However, many of these approaches entail limitations, such as the high cost of the sophisticated instruments required, the incompatibility with in situ analyses, the lack of standardisation in the case of EVs, and the fact that large volumes of samples are often required [ 14 ].…”