Salt gradient separation and analysis of adeno-associated virus samples using a 3 μm monodisperse strong anion exchange chromatography column

Significance of the Topic

Adeno-associated virus (AAV) vectors are critical in gene therapy, requiring precise quantification of empty versus DNA-filled capsids to ensure safety and potency. Traditional ultracentrifugation techniques are laborious and time-consuming, making high-resolution chromatographic approaches attractive for routine quality control and analytical workflows in biopharmaceutical development.

Goals and Study Overview

This application note demonstrates the development and optimization of salt gradient strong anion exchange (SAX) chromatography methods for separating and quantifying empty and full AAV capsids. Using a 2 × 50 mm ProPac 3R SAX column with monodisperse 3 µm resin, the study evaluates a simple linear gradient and an enhanced method incorporating an isocratic hold to improve resolution.

Methodology and Instrumentation

• Sample Preparation and Reagents: empty and full AAV serotypes 1, 6, and 8 at 2×10^13 vg/mL mixed 1:10 for initial tests; mobile phases: water, 1 M tetramethylammonium chloride, 200 mM BIS-TRIS propane pH 9.0
• Chromatographic System: Vanquish Flex quaternary UHPLC system with fluorescence detection (Ex 280 nm, Em 330 nm); ProPac 3R SAX, 3 µm monodisperse resin, 2 × 50 mm column at 20 °C, 0.2 mL/min flow; fluorescence detection enhances sensitivity for low sample loads

Results and Discussion

Linear Salt Gradient: a gradient from 12% to 32% mobile phase B over 15 minutes baseline-resolved empty and full capsids for AAV1, AAV6, and AAV8, with co-eluting impurities identified. Lot-to-lot reproducibility was confirmed across three resin batches.

Isocratic Hold Enhancement: introducing an isocratic hold at around 17% mobile phase B improved separation of AAV6 empty and full capsids (resolution up to 4.1). Optimizing hold concentration and duration (e.g., 17% for 4 min) balanced peak sharpness and symmetry.

Practical Benefits and Applications

• High-resolution, reproducible separation supports robust QC in gene therapy manufacturing
• Short column length and monodisperse resin allow fast turnaround and low sample consumption
• Fluorescence detection ensures sensitivity when sample is limited

Future Trends and Opportunities

Emerging opportunities include integration of SAX chromatography with multi-detector platforms (e.g., light scattering, mass spectrometry) for orthogonal confirmation of capsid composition. Advances in stationary phase chemistries and automated gradient optimization will streamline method development. Adapting these approaches for other viral vectors and continuous bioprocess monitoring represents a promising direction.

Conclusion

Monodisperse SAX chromatography on the ProPac 3R SAX column provides an efficient, reproducible platform for separating and quantifying empty and full AAV capsids. Both simple linear gradients and methods with isocratic holds can be tailored to different serotypes, offering a versatile tool for gene therapy analytics.

Instrumentation Used

• Thermo Scientific Vanquish Flex Quaternary UHPLC system
• ProPac 3R SAX, 3 µm, 2 × 50 mm column
• Fluorescence detector (Ex 280 nm, Em 330 nm)

References

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