Enhancing the Stabilization Potential of Lyophilization for Extracellular Vesicles
![Figure 1. Characterization of RO EVs and SBCy050 OMVs by cryo-TEM, both directly after ultracentrifugation (A and C) and after an additional step of SEC-purification (B and D). Red arrows point to vesicular structures, while white arrows indicate non-vesicular structures and cell debris. Panels E and F show the analysis of RO EVs by flow cytometry (FACS). RO EVs are positive for both CD9 (E) and CD63 (F).](https://www.pharmaexcipients.com/wp-content/uploads/2021/08/Enhancing-the-Stabilization-Potential-of-Lyophilization-for-Extracellular-Vesicles.png)
Extracellular vesicles (EV) are an emerging technology as immune therapeutics and drug delivery vehicles. However, EVs are usually stored at −80 °C which limits potential clinical applicability. Freeze-drying of EVs striving for long-term stable formulations is therefore studied. The most appropriate formulation parameters are identified in freeze-thawing studies with two different EV types. After a freeze-drying feasibility study, four lyophilized EV formulations are tested for storage stability for up to 6 months.
Freeze-thawing studies revealed improved colloidal EV stability in presence of sucrose or potassium phosphate buffer instead of sodium phosphate buffer or phosphate-buffered saline. Less aggregation and/or vesicle fusion occurred at neutral pH compared to slightly acidic or alkaline pH. EVs colloidal stability can be most effectively preserved by addition of low amounts of poloxamer 188. Polyvinyl pyrrolidone failed to preserve EVs upon freeze-drying. Particle size and concentration of EVs are retained over 6 months at 40 °C in lyophilizates containing 10 mm K- or Na-phosphate buffer, 0.02% poloxamer 188, and 5% sucrose.
The biological activity of associated beta-glucuronidase is maintained for 1 month, but decreased after 6 months. Here optimized parameters for lyophilization of EVs that contribute to generate long-term stable EV formulations are presented.
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Article information: Enhancing the Stabilization Potential of Lyophilization for Extracellular Vesicles. Adv. Healthcare Mater. 2021, 2100538. https://doi.org/10.1002/adhm.202100538
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