Exosomes are small membrane-bound vesicles that are secreted by cells and play a role in intercellular communication. They contain a variety of biomolecules, including proteins, lipids, and nucleic acids, and are increasingly being studied as potential biomarkers and therapeutic targets. Proper storage of isolated exosomes is critical to maintaining their integrity and ensuring their suitability for downstream applications. In this answer, we will discuss the best storage conditions for isolated exosomes.
Temperature
The temperature at which exosomes are stored is a critical factor in their stability and integrity. Exosomes are sensitive to temperature fluctuations and can degrade rapidly if not stored at the appropriate temperature. It is generally recommended to store exosomes at -80°C to maintain their stability for long-term storage. However, if long-term storage is not needed, exosomes can be stored at -20°C for up to 6 months. It is important to avoid repeated freeze-thaw cycles, as this can lead to aggregation and degradation of the exosomes.
Buffer
The buffer used to store exosomes can also impact their stability and integrity. Exosomes should be stored in a buffer that maintains their physiological pH and osmolarity. Commonly used buffers for exosome storage include phosphate-buffered saline (PBS), sucrose, and trehalose. PBS is a widely used buffer for exosome storage and is recommended for short-term storage at 4°C. Sucrose and trehalose are both disaccharides that have been shown to stabilize exosomes during freeze-thaw cycles and are recommended for long-term storage at -80°C.
Contamination
Contamination is a major concern when storing exosomes, as any contamination can impact their biological activity and downstream applications. To minimize contamination, it is recommended to store exosomes in sterile tubes and avoid opening the tubes unnecessarily. If possible, it is also recommended to store exosomes in aliquots to avoid repeated freeze-thaw cycles.
Freezing and Thawing
Freezing and thawing can also impact the stability and integrity of exosomes. Exosomes should be frozen quickly to minimize ice crystal formation, which can damage the membrane structure of the exosomes. Rapid freezing can be achieved by placing the exosomes in a dry ice/ethanol bath or a -80°C freezer. When thawing exosomes, it is important to avoid rapid temperature changes, as this can lead to the formation of ice crystals. Exosomes should be thawed slowly at 4°C or on ice.
Quality Control
Before storing exosomes, it is important to perform a quality control check to ensure that they are suitable for downstream applications. Quality control checks can include measuring the size distribution and concentration of the exosomes using techniques such as nanoparticle tracking analysis (NTA) or dynamic light scattering (DLS). It is also important to confirm the presence of exosomal markers, such as CD63 or CD81, using Western blot or flow cytometry.
In conclusion, proper storage conditions are critical to maintaining the stability and integrity of isolated exosomes. Exosomes should be stored at -80°C in a buffer that maintains their physiological pH and osmolarity. Contamination should be minimized, and freezing and thawing should be done carefully to avoid damage to the exosomes. Quality control checks should be performed before storing exosomes to ensure their suitability for downstream applications. By following these guidelines, researchers can ensure that their isolated exosomes are stored properly and are suitable for future use.
