Preservation methods currently used for long-term exosome storage primarily include cryopreservation, freeze-drying, and spray-drying.
Temperature and antifreeze are the most important components of cryopreservation. Storage at 4°C can impair biological activity and reduce protein charge in exosomes, while -80°C is considered the optimal temperature, causing minimal impact on exosome shape and content.
Non-permeable disaccharide antifreeze, particularly trehalose, represents the best option because it prevents exosome aggregation and cryodamage.
Heat-sensitive materials, such as exosomes and vaccines, can be easily stored by lyophilization and freeze-drying and can be reconstituted simply by adding water.
A recent study demonstrated that lyophilization using a cryoprotectant can preserve the activity of exosome proteins and RNA for approximately 4 weeks, even when stored at room temperature.
Finally, in contrast to freeze-drying, spray drying is a one-step process, eliminating the need for expensive equipment and lengthy, multi-step grinding. However, key parameters of spray drying, such as exosome feed rate, dissolution pressure, and outlet temperature, can all affect exosome stability and product safety.
