Two-Dimensional Liquid Chromatography Isolation and Quantitation of IgG and Exosomes from Cell Culture Media

Significance of the Topic

Advances in biologics production and extracellular vesicle research demand robust analytical workflows capable of extracting multiple high-value products from complex cell culture media. Two-dimensional liquid chromatography (2D-LC) offers a promising solution by coupling affinity capture of monoclonal antibodies with downstream hydrophobic interaction chromatography to isolate both IgG and exosomes in a single integrated process.

Study Objectives and Overview

This work aimed to develop and validate a 2D-LC method that:

• Recovers therapeutic IgG from CHO cell culture supernatants via Protein A affinity on capillary-channeled polymer fibers (C-CP).
• Recovers and purifies exosomes from the Protein A effluent using a second dimension hydrophobic interaction chromatography (HIC).
• Demonstrates quantitative performance, high purity, and feasibility for process analytical technology (PAT) integration.

Methodology and Instrumentation

The process employed two sequential separation dimensions:

• Dimension 1 (1D): Protein A affinity chromatography on polypropylene C-CP fiber columns, eluted by pH gradient to capture IgG selectively.
• Dimension 2 (2D): Hydrophobic interaction chromatography on polyester C-CP fibers with an inverse salt/organic modifier gradient to retain and elute exosomes.

Instrumentation included:

• Two HPLC pumps delivering mobile phases for each dimension.
• A modular 2D switch for timed transfer of 1D effluent to 2D loop.
• UV detectors for IgG quantitation in 1D and exosome quantitation in 2D.
• Custom C-CP fiber columns (PP for Protein A, PET for HIC) mounted in capillaries.

Results and Discussion

IgG Performance:

• Recovery linear over 1–8 µg injections (R² = 0.99).
• Yield exceeded 95% with RSD <5%.
• Purity confirmed by SDS-PAGE, comparable to commercial columns.

Exosome Performance:

• Average particle diameter 83 ± 23 nm by nano-flow cytometry.
• Immunolabeling showed ~66% tetraspanin‐positive vesicles (CD9, CD63, CD81).
• Membrane staining indicated ~93% vesicle integrity.
• Recovery of ~1.8×10¹¹ particles/mL with <7% RSD.
• Host cell protein content reduced by >99% (3 mg/mL to 3 µg/mL).
• Purity >5×10¹⁰ particles/µg protein, meeting NIH guidelines.

Benefits and Practical Applications

This approach enables concurrent capture of therapeutic antibodies and high-purity exosomes from the same bioreactor harvest, delivering:

• Resource recovery by valorizing the Protein A effluent.
• Enhanced PAT capabilities for real-time monitoring of cell culture health and productivity.
• Cost savings using inexpensive C-CP fiber columns (<$5 each) with in-house chemistry modification.

Future Trends and Potential Applications

Potential extensions include:

• Analytical scale C-CP columns for high-throughput screening.
• Isotopic labeling (e.g., Yb) of exosomes for ICP-MS quantitation.
• Functional assays of HIC-isolated exosomes in cellular uptake studies.
• Anion exchange chromatography using polymer fiber modifications.
• Adaptations for liposome and adeno-associated virus (AAV) separations.

Conclusion

The developed 2D-LC workflow successfully integrates Protein A affinity and HIC on capillary-channeled polymer fiber columns to isolate and quantify both therapeutic IgG and exosomes from CHO supernatant. The method achieves high yield, purity, and reproducibility using cost-effective materials, offering a scalable platform for downstream processing and advanced bioprocess analytics.