Exosome Isolation: Cyclical Electrical Field Flow Fractionation in Low-Ionic-Strength Fluids.

Area of Science:

• Biotechnology
• Nanotechnology
• Analytical Chemistry

Background:

• Exosomes are crucial biomarkers and therapeutic agents, necessitating precise isolation and characterization methods.
• Current exosome isolation techniques can be influenced by buffer composition and sample dilution, affecting downstream analysis.
• Cyclical electrical field flow fractionation (Cy-El-FFF) presents a label-free technique for particle separation based on size and charge.

Purpose of the Study:

• To investigate the effects of buffer substitution and dilution on exosome size and electrophoretic mobility using Cy-El-FFF.
• To evaluate the influence of different carrier fluids on the isolation efficiency and fractogram patterns of A375 melanoma exosomes.
• To compare the separation behavior of exosomes with synthetic particles in various low-ionic-strength buffers.

Main Methods:

• Exosomes and other particles were subjected to Cy-El-FFF using carrier fluids including deionized (DI) water, phosphate-buffered saline (PBS), trehalose, and isopropyl alcohol (IPA).
• Fractograms were analyzed to observe retention time trends with varying AC voltage.
• Exosome recovery rates and electrophoretic mobility were measured under different buffer conditions and dilution factors.

Main Results:

• All tested carrier fluids influenced Cy-El-FFF-mediated isolation of A375 melanoma exosomes, with consistent recovery rates (70-80%) across buffer substitutions.
• Exosome dilution in DI water showed a U-shaped dependence on electrophoretic mobility, while dilution in PBS resulted in a gradual change.
• A maximum retention time at approximately 1.3 V AC was observed across all fractograms, indicating consistent behavior under varying voltage.

Conclusions:

• Buffer composition and dilution significantly alter exosome electrophoretic mobility and separation dynamics in Cy-El-FFF.
• Cy-El-FFF is a highly promising label-free technology for cataloging and purifying exosome subtypes for biobanking and further interrogation.
• The findings provide critical insights for optimizing Cy-El-FFF protocols for accurate exosome analysis and subtype characterization.