How are they characterized?

Exosome characterization can be accomplished using these strategies: 

Electron microscopy – Electron microscopy enables scientists to visualize the size and morphology of exosomes. This technique can also be used together with immune labeling to observe specific exosome features such as surface proteins. 

Nanoparticle tracking analysis - Nanoparticle tracking analysis is a biophysical approach that detects the path of exosomal movement to measure the velocity of the particles. This approach allows scientists to estimate the concentration and size distribution of exosomes in the 10 nm to 2 µm range. 

Flow cytometry - Based on a molecular approach, flow cytometry is among the most commonly used techniques to characterize exosomal surface proteins and to measure the size and structure of exosomes. 

Dynamic light scattering (DLS) analysis - Also known as photon correlation spectroscopy, DLS analysis measures the size of exosomes by passing a monochromatic coherent laser beam through a suspension of particles and analyzing their unique light scattering patterns. 

Atomic force microscopy – Atomic force microscopy offers scientists a unique and reliable technique for characterizing exosomes by detecting and recording interactions between the sample surface and a probing tip. A key advantage that this technique offers is the ability to measure samples in native conditions with minimum sample preparation and no destructive operation mode. 

Mass spectrometry – Mass spectrometry is typically used to identify protein cargo in exosomes, and detect the presence of contaminants such as protein aggregates in the sample. 

Resistive Pulse Sensing – A relatively new technique for characterizing exosomes, resistive pulse sensing is particularly useful for measuring exosome concentration and size distribution.