Profiling Poloxamer Oxidation in Adeno-Associated Virus Formulations

Significance of the topic

Poloxamer 188 is increasingly used as a nonionic surfactant in biopharmaceutical formulations to protect proteins and viral vectors from interfacial stress, aggregation, and particle formation. While poloxamers avoid ester hydrolysis pathways that affect polysorbates, they remain vulnerable to oxidative degradation—particularly within the poly(propylene oxide) (PPO) block—leading to polymer backbone cleavage, formation of low molecular weight fragments, altered surfactant performance, and potential impacts on product quality and stability. Rapid, practical analytical screening methods are therefore important for formulation development, risk assessment, and ongoing monitoring of critical quality attributes (CQAs) in therapeutic proteins and AAV-based products.

Objectives and overview of the study

The application note demonstrates a streamlined LC–MS screening workflow for detecting oxidative degradation of poloxamer 188 in both neat solutions and an AAV8 formulation. The aims were to develop MS-compatible chromatographic conditions, optimize single‑quadrupole MS source parameters for this nonionic polymer, and show the method's ability to detect qualitative degradation trends induced by Fenton oxidative stress across timepoints.

Methodology

• Stress conditions: Oxidative degradation was induced mainly via the Fenton reaction (H2O2 + FeCl3) at 25 °C with aliquots collected at T0, 1 day, and 10 days. Controls included H2O2-only and iron-only incubations.
• Sample handling: Stressed and control samples (neat poloxamer and AAV8 formulation) were placed in HPLC vials and directly injected without extensive cleanup.
• Chromatographic strategy: Short, MS‑compatible gradients were prioritized to deliver sharp poloxamer peaks in the aqueous/organic window suitable for MS detection and to provide space in the chromatogram to resolve potential degradation-related pre‑peaks.
• Key analytical observations: Acetonitrile as organic modifier reduced late retention compared with methanol and improved MS signal and chromatographic placement of the main poloxamer peak; acidic volatile buffers (0.1% formic acid) provided best balance between chromatographic performance and MS compatibility.

Instrumentation used

• Agilent 1290 Infinity III LC system (Bio High-Speed Pump, Bio Multisampler, Multicolumn Thermostat) with 1290 Infinity II Diode Array Detector.
• AdvanceBio Surfactant Profiling HPLC column, 2.1 × 100 mm, 3.5 µm, with matching guard column.
• Agilent InfinityLab Pro iQ Series single quadrupole mass detector (Pro iQ Plus, G6170A) operated in positive ESI mode.
• Data system: Agilent OpenLab CDS (version 2.8) used for data acquisition and systematic source-parameter variation.
• Representative MS settings: ESI positive; gas temperature 200 °C; nebulizer 30 psi; gas flow 12 L/min; capillary voltage 3000 V; fragmentor 150 V; scan m/z 100–2000; scan time ~1512 ms.
• LC method summary: Mobile phase A = 0.1% formic acid in water; Mobile phase B = 0.1% formic acid in acetonitrile; flow 0.6 mL/min; column 50 °C; gradient 5→95% B in 4 minutes; needle wash 1:1 methanol:water.

Main results and discussion

• Chromatographic markers of degradation: Fenton-treated samples developed a reproducible earlier‑eluting shoulder peak preceding the main poloxamer peak, accompanied by a progressive loss of main-peak intensity over days. This signature was evident in both neat poloxamer and AAV formulation, though the degradation response in formulation was attenuated relative to neat polymer.
• Mass spectral evidence: Spectra from the earlier eluting shoulder showed a shift toward lower m/z populations compared to the intact main peak. Extracted spectra from shoulder regions revealed numerous mass losses consistent with repeat-unit cleavages—losses of ~44 Da (PEO unit) and ~58 Da (PPO unit)—supporting polymer chain scission as the degradation mechanism.
• Optimization outcomes: Acetonitrile improved chromatographic placement and MS response relative to methanol. MS source optimization identified fragmentor = 150 V and capillary = 3000 V as conditions providing high total ion current without significant in‑source fragmentation.
• Quantitative reproducibility in screening: The early-eluting degradation peak showed acceptable reproducibility in stressed formulation samples, with percent CVs for shoulder peak height of ~3.5% (T1) and ~4.1% (T10), supporting the method's utility as a comparative screening assay.
• Matrix effects: Degradation signatures were qualitatively similar in AAV formulation despite reduced magnitude, indicating that the method can detect oxidative changes in complex biopharma matrices without extensive sample cleanup; AAV signal likely elutes in the void and did not interfere under the chosen conditions.

Benefits and practical applications of the method

• Rapid screening: A short gradient and direct injection enable quick screening of many stress or formulation samples during development.
• Simplified data interpretation: Clear chromatographic markers (main peak loss and earlier-eluting shoulder) combined with characteristic mass shifts allow straightforward detection of oxidative degradation trends.
• MS compatibility: Use of volatile acidic mobile phases and optimized ESI parameters permits direct coupling to a single‑quad MS detector for routine lab workflows without requiring high‑resolution instruments.
• Broad applicability: Method suitable for formulation development work, forced‑degradation studies, excipient CQA monitoring, and comparative studies of surfactant stability in different formulation matrices (e.g., protein therapeutics, viral vectors).

Future trends and applications

• Advancing to higher structural detail: Complementary use of high-resolution MS or tandem MS would enable more definitive identification of specific cleavage products and end groups.
• Quantitation and method qualification: Development of validated quantitation approaches (e.g., using labeled internal standards or orthogonal separation) would convert this screening workflow into a regulated stability assay for CQAs.
• Integration with other assays: Combining surfactant degradation profiling with particle analysis, peptide mapping, and potency assays will provide a fuller risk assessment for formulation performance.
• Automation and high-throughput monitoring: Short LC runs and direct-injection workflows are amenable to automation for routine stability screening across multiple formulations and lots.
• Regulatory and comparability applications: As poloxamers replace polysorbates in some products, robust analytical control strategies will be needed to address oxidative degradation risks and support regulatory submissions.

Conclusion

The reported workflow—AdvanceBio Surfactant Profiling LC coupled to an Agilent InfinityLab Pro iQ single‑quadrupole MS—provides a practical, MS‑compatible screening approach to detect oxidative degradation of poloxamer 188. Chromatographic and mass spectral signatures (loss of main peak, earlier-eluting shoulder, shift to lower m/z with repeated losses of 44 and 58 Da) collectively indicate polymer backbone cleavage under Fenton stress. The method reliably detects qualitative degradation trends in both neat and formulated samples and serves as an efficient tool for formulation screening, stress testing, and proactive monitoring of surfactant‑related CQAs.

References

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