Exosome-based products
are gaining momentum in diagnostics, therapeutics, and regenerative medicine,
but their clinical and research utility depends on maintaining their stability
during storage and handling. Recent research provides important insights into
how exosomes can be best preserved to retain their structure, biological
activity, and functional cargo.
Why Exosome Stability Matters
Exosomes are delicate,
biologically active vesicles. Improper storage or repeated handling can damage
their membranes, degrade their contents, and diminish their therapeutic or
diagnostic efficacy. Stability evaluation is essential for:
- Ensuring consistent product quality for
clinical and research applications
- Comparing the effectiveness of different
exosome preparation and storage methods
- Meeting regulatory requirements for
product development and commercialization1
Key
Factors Affecting Exosome Stability
1. Preparation
Method
Different isolation techniques, such as ultracentrifugation, ultrafiltration,
affinity chromatography, and precipitation, yield exosomes with varying degrees
of purity and integrity. Some methods may inadvertently damage exosomes,
impacting their stability and downstream applications1.
2. Storage
Temperature
Temperature is a critical determinant of exosome stability:
- Room Temperature and 4°C: Short-term storage at 4°C is
acceptable for a few days, but exosomes degrade rapidly over longer
periods, with losses in protein content and functional activity 2-3-4.
- −20°C: Offers better preservation than 4°C for short-term storage,
but long-term storage still results in decreased quantity and altered size
distribution 4-5.
- −80°C: The consensus for long-term storage. Exosomes remain
structurally stable and retain their protein and RNA cargo for months to
years when stored at −80°C, with minimal impact from freeze-thaw cycles if
handled properly 2-3-4-5.
3. Storage Buffer
Composition
Phosphate-buffered saline (PBS) is commonly used, but studies show that
exosomes stored in PBS alone can suffer significant losses in recovery and
function, especially after freeze-thaw cycles 3-5.
- Supplementing PBS with human albumin and
trehalose (PBS-HAT) or other cryoprotectants like DMSO improves exosome
stability, preserves cargo, and enhances recovery after freezing 3-5.
4. Freeze-Thaw
Cycles
Repeated freeze-thawing can damage exosome membranes and reduce their
bioactivity. While some studies report minimal changes in size after several
cycles, others show that freeze-thawing should be minimized to preserve
functional integrity, especially for therapeutic use 2-4-5.
5. Storage Duration
Exosomes are stable for at least 3 months at −80°C, and some studies report
preservation up to 2 years with optimized buffers and storage conditions 2-3. However, freshly isolated exosomes are
always preferred for functional studies and clinical applications 4.
Practical
Recommendations
- For short-term storage (up
to one week), 4°C may be used, but only if exosomes will be analyzed
quickly.
- For long-term storage, −80°C
is strongly recommended, ideally with cryoprotectants like trehalose or
human albumin in the buffer to maximize stability and recovery 3-5.
- Avoid repeated freeze-thaw cycles; aliquot
exosome preparations to minimize handling.
- Use siliconized vessels to prevent exosome
adherence to container walls5.
- Always validate storage protocols for each
exosome product and intended application 1-3-5.
Conclusion
The stability and
storage of exosome products are influenced by isolation method, storage
temperature, buffer composition, and handling practices. Research consistently
supports −80°C storage with protective additives as the gold standard for
preserving exosome integrity and function. As exosome-based therapies and
diagnostics move toward mainstream clinical use, rigorous stability evaluation
and optimized storage protocols will be essential for ensuring safety,
efficacy, and reproducibility.
References:
1 Creative Biolabs: Stability Evaluation
Service for Exosome Product
2 PMC: Exosomes in bodily fluids are a
highly stable resource of disease biomarkers
3 PMC: Identification of storage conditions
stabilizing extracellular vesicles
4 PMC: Preservation of small extracellular
vesicles for functional analysis
5 Izon Science: How to Store Extracellular
Vesicles