Neutrophil extracellular traps are networks of DNA and associated proteins produced by nucleosome release from activated neutrophils in response to infection stimuli and have recently been identified as key mediators between innate immunity, inflammation, and hemostasis. The interaction of DNA and histones with a number of hemostatic factors has been shown to promote clotting and is associated with increased thrombosis, but little is known about the effects of DNA and histones on the regulation of fibrin stability and fibrinolysis. Here we demonstrate that the addition of histone-DNA complexes to fibrin results in thicker fibers (increase in median diameter from 84 to 123 nm according to scanning electron microscopy data) accompanied by improved stability and rigidity (the critical shear stress causing loss of fibrin viscosity increases from 150 to 376 Pa whereas the storage modulus of the gel increases from 62 to 82 pascals according to oscillation rheometric data). The effects of DNA and histones alone are subtle and suggest that histones affect clot structure whereas DNA changes the way clots are lysed. The combination of histones + DNA significantly prolongs clot lysis. Isothermal titration and confocal microscopy studies suggest that histones and DNA bind large fibrin degradation products with 191 and 136 nm dissociation constants, respectively, interactions that inhibit clot lysis. Heparin, which is known to interfere with the formation of neutrophil extracellular traps, appears to prolong lysis time at a concentration favoring ternary histone-DNA-heparin complex formation, and DNase effectively promotes clot lysis in combination with tissue plasminogen activator.

Cell‐derived or extracellular vesicles, including microparticles and exosomes, are abundantly present in body fluids such as blood. Although such vesicles have gained strong clinical and scientific interest, their detection is difficult because many vesicles are extremely small with a diameter of less than 100 nm, and, moreover, these vesicles have a low refractive index and are heterogeneous in both size and composition. In this review, we focus on the relatively high throughput detection of vesicles in suspension by flow cytometry, resistive pulse sensing, and nanoparticle tracking analysis, and we will discuss their applicability and limitations. Finally, we discuss four methods that are not commercially available: Raman microspectroscopy, micro nuclear magnetic resonance, small‐angle X‐ray scattering (SAXS), and anomalous SAXS. These methods are currently being explored to study vesicles and are likely to offer novel information for future developments.

Background: Extracellular vesicles (EVs) have clinical importance due to their roles in a wide range of biological processes. The detection and characterization of EVs are challenging because of their small size, low refractive index, and heterogeneity.Methods: In this manuscript, the size distribution of an erythrocyte‐derived EV sample is determined using state‐of‐the‐art techniques such as nanoparticle tracking analysis, resistive pulse sensing, and electron microscopy, and novel techniques in the field, such as small‐angle X‐ray scattering (SAXS) and size exclusion chromatography coupled with dynamic light scattering detection.Results: The mode values of the size distributions of the studied erythrocyte EVs reported by the different methods show only small deviations around 130 nm, but there are differences in the widths of the size distributions.Conclusion: SAXS is a promising technique with respect to traceability, as this technique was already applied for traceable size determination of solid nanoparticles in suspension. To reach the traceable measurement of EVs, monodisperse and highly concentrated samples are required.

Size characterization of extracellular vesicles (EVs) and drug delivery liposomes is of great importance in their applications in diagnosis and therapy of diseases. There are many different size characterization techniques used in the field, which often report different size values. Besides technological biases, these differences originate from the fact that various methods measure different physical quantities to determine particle size. In this study, the size of synthetic liposomes with nominal diameters of 50nm and 100nm, and red blood cell-derived EVs (REVs) were measured with established optical methods, such as dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA), and with emerging non-optical methods such as microfluidic resistive pulse sensing (MRPS) and very small-angle neutron scattering (VSANS). The comparison of the hydrodynamic sizes obtained by DLS and NTA with the sizes corresponding to the excluded volume of the particles by MRPS enabled the estimation of the thickness of the hydration shell of the particles. The comparison of diameter values corresponding to the boundary of the phospholipid bilayer obtained from VSANS measurements with MRPS size values revealed the thickness of the polyethylene glycol-layer in case of synthetic liposomes, and the thickness of the protein corona in case of REVs.

The surface charge density of nanoparticles plays an important role in the way they interact with biological systems. The ability to measure the surface charge density of nanoparticles in biological media is therefore of importance in understanding the magnitude of such interactions. There are a number of methods which may be used to assess surface charge density through the measurement of electrophoretic mobility. In order to better understand the comparability of these methods, the ζ-potential of silica nanoparticles in water, buffer and serum-based biological medium was measured by one ensemble and two particle-by-particle techniques: electrophoretic light scattering (ELS), tunable resistive pulse sensing (TRPS) and zeta particle tracking analysis (z-PTA). To allow the comparability of results from different techniques, test samples were prepared according to an established protocol, although some variations were necessary to meet specific instrument requirements. Here we compare, for the first time, measurement results from the different techniques and discuss how modifications related to parameters such as environmental pH, dilution factor and presence of biomolecules influence the charge measurements.