Advancements in extracellular vesicle (EV) studies necessitate the development of optimized storage conditions to ensure preservation of physical and biochemical characteristics. In this study, the most common buffer for EV storage (phosphate-buffered saline/PBS) was compared to a cryoprotective 5% sucrose solution. The size distribution and concentration of EVs from two different sources changed to a greater extent after −80 °C storage in PBS compared to the sucrose solution. Additionally, molecular surface protrusions and transmembrane proteins were more prevalent in EVs stored in the sucrose solution compared to those stored in PBS. This study demonstrates, for the first time, that distinct ring-like molecular complexes and cristae-like folded membranous structures are visible upon EV degradation. Taken together, the size, concentration, molecular surface extensions, and transmembrane proteins of EVs varied substantially based on the buffer used for −80 °C storage, suggesting that biocompatible cryoprotectants, such as sucrose, should be considered for EV studies.

Living organisms compartmentalize their catalytic reactions in membranes for increased efficiency and selectivity. To mimic the organelles of eukaryotic cells, we develop a mild approach for in situ encapsulating enzymes in aqueous‐core silica nanocapsules. In order to confine the sol‐gel reaction at the water/oil interface of miniemulsion, we introduce an aminosilane to the silica precursors, which serves as both catalyst and an amphiphilic anchor that electrostatically assembles with negatively charged hydrolyzed alkoxysilanes at the interface. The semi‐permeable shell protects enzymes from proteolytic attack, and allows the transport of reactants and products. The enzyme‐carrying nanocapsules, as synthetic nano‐organelles, are able to perform cascade reactions when enveloped in a polymer vesicle, mimicking the hierarchically compartmentalized reactions in eukaryotic cells. This in situ encapsulation approach provides a versatile platform for the delivery of biomacromolecules.

The variable presence of contaminants in extracellular vesicle (EV) samples is one of the major contributors to a lack of inter‐study reproducibility in the field. Well‐known contaminants include protein aggregates, RNA‐protein complexes and lipoproteins, which resemble EVs in shape, size and/or density. On the contrary, polysaccharides, such as hyaluronic acid (HA), have been overlooked as EV contaminants. Here, it is shown that low and medium molecular weight HA polymers are unexpectedly retained to some extent in EV fractions using two common isolation methods known for high purity: size‐exclusion chromatography and tangential flow filtration. Although these isolation techniques are capable of efficient removal of non‐EV‐associated proteins, this is not the case for HA polymers, which are partially retained in a molecular weight‐dependent manner, especially with size‐exclusion chromatography. The supramolecular structure and hydrodynamic size of HA are likely to contribute to isolation in EV fractions of filtration‐based approaches. Conversely, HA polymers were not retained with ultracentrifugation and polymer‐based precipitation methods, which are known for co‐isolating other types of contaminants. HA has a broad range of immunomodulatory effects, similar to those ascribed to various sources of EVs. Therefore, HA contaminants should be considered in future studies to avoid potential inaccurate attributions of functional effects to EVs.