High-throughput exosome isolation based on bidirectional flow control through nanoporous membrane

Exosomes, tiny vesicles released by cells, have garnered significant attention in biomedical research for their potential as biomarkers in liquid biopsy—a non-invasive diagnostic approach. These vesicles carry various biomolecules such as proteins and RNA, reflecting the physiological state of their parent cells. However, isolating exosomes efficiently from biological samples has proven challenging due to their small size range, typically spanning from 50 to 200 nanometers (nm).

Introducing Bidirectional Flow Control Filtration (BFF)

In a recent study, researchers at Korea University have proposed a novel method called bidirectional flow control filtration (BFF) to address these challenges. The BFF method utilizes nanoporous membranes made from polycarbonate, featuring two distinct pore sizes: 200 nm and 50 nm. This dual membrane setup allows for precise isolation of exosomes while excluding larger particles and soluble proteins that might interfere with exosome purity.

How BFF Works

  1. Membrane Selection: A membrane with 200 nm pores first filters out larger particles like apoptotic bodies, ensuring that the sample is free from contaminants that could obscure exosome analysis.
  2. Concentration Step: Subsequently, a membrane with 50 nm pores concentrates exosomes, effectively removing smaller proteins and further purifying the sample.
  3. Backflush Maneuvers: To prevent pore clogging during both phases, backflush maneuvers are employed. This technique helps maintain the integrity and efficiency of the filtration process, crucial for consistent exosome isolation.

Comparative Performance

The effectiveness of BFF was validated through comparative studies:

  • Higher Purity: BFF achieved purity ratios 26 times higher than ultracentrifugation and 19 times higher than direct-flow filtration when isolating exosomes from adipose tissue samples.
  • Improved Recovery: A recovery rate of 68% was achieved, indicating efficient capture and retention of exosomes during the filtration process.
  • Superior to Chromatography: Compared to size-exclusive chromatography, BFF demonstrated 4.4-fold higher purity and 1.9-fold higher throughput when isolating exosomes from human serum.

Advantages and Applications

  1. Scalability: BFF is scalable and capable of processing up to 1 liter of sample per hour, making it suitable for large-scale production of exosomes for therapeutic applications.
  2. Minimal Physical Stress: Unlike methods involving ultracentrifugation or harsh chemical treatments, BFF minimizes physical stress on exosomes, preserving their structural and functional integrity.
  3. Chemical Additive-Free: The method does not require chemical additives, ensuring that isolated exosomes remain free from contaminants that could affect downstream applications.

Conclusion

The development of BFF represents a significant advancement in exosome isolation technology. Its ability to achieve high purity, efficient recovery rates, scalability, and minimal impact on exosome integrity positions it as a promising tool for both research and clinical applications. By enabling reliable isolation of exosomes from complex biological samples, BFF opens doors to new possibilities in disease diagnosis, monitoring, and therapeutic development, paving the way for personalized medicine approaches based on exosome biomarkers. In essence, BFF not only enhances our understanding of exosome biology but also accelerates the translation of exosome research into practical healthcare solutions.

Kim G, Kim KH, Seo M, Kim T, Chun H. (2024) High-throughput exosome isolation based on bidirectional flow control through nanoporous membrane. Sens Act B: Chem [Epub ahead of print]. [article]

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