Recombinant Albumin Preserves Dilute Cytokine Recovery and Bioactivity at Room Temperature

Published on 23 April 2026

Poster

Dilute cytokines lose activity during routine handling because of surface adsorption, aggregation, and oxidative degradation — losses that introduce variability into cell therapy and biomanufacturing workflows. In a 4-week stability study across refrigerated (2–8°C), room-temperature, and elevated (35–40°C) conditions, InVitria® evaluated whether Optibumin® 25, a recombinant human serum albumin (rHSA) produced in a non-mammalian expression system, could stabilize a model cytokine at 10 µg/mL and 100 µg/mL. Monomer recovery was measured by capillary electrophoresis (ProteinSimple Wes); bioactivity was measured by EC50 in a cytokine-responsive cell proliferation assay. Optibumin 25 preserved approximately 20% higher cytokine recovery at 2–8°C and up to 50% higher recovery at room temperature versus formulations without albumin, while matching the performance of plasma-derived HSA — without the lot-to-lot variability, viral contamination risk, or inconsistent redox profiles of donor-derived material.

Key Findings

The study established four findings with direct implications for cytokine handling in cell therapy manufacturing and biologics workflows:

• Optibumin 25 preserved cytokine monomer recovery at dilute concentrations across 4 weeks of storage at both 2–8°C and room temperature
• Bioactivity (EC50) was maintained at room temperature when Optibumin 25 was included, while no-albumin controls showed approximately 4× loss of potency
• At 4°C, no-albumin controls showed approximately 2× loss of bioactivity, while Optibumin 25 preserved activity
• Optibumin 25 performance was comparable to plasma-derived HSA across all recovery and bioactivity endpoints, without the risks associated with donor-derived material

Why Dilute Cytokines Are Unstable

Cytokines and growth factors are critical regulators of cell expansion, activation, and differentiation, and are among the most expensive and sensitive components in cell culture systems. At the low µg/mL and ng/mL concentrations typical of cell therapy and biomanufacturing workflows, cytokines become highly susceptible to loss during routine handling, storage, and temperature fluctuations.
Three mechanisms drive this instability. Surface adsorption causes cytokines to bind irreversibly to container walls and pipette tips. Hydrophobic regions on the cytokine surface drive aggregation into inactive multimers. Oxidative degradation damages functional residues over time. Each mechanism is amplified at dilute concentrations where cytokine molecules are vastly outnumbered by available binding and reactive surfaces.
Albumin mitigates all three mechanisms. It acts as a sacrificial carrier protein that competes for adsorption sites, shields hydrophobic surfaces to prevent aggregation, and buffers against oxidation through its free thiol groups. The result is preserved cytokine recovery and preserved functional potency across storage conditions.
Plasma-derived human serum albumin has historically been used for this stabilization role, but donor-derived material introduces lot-to-lot variability, residual viral contamination risk, and inconsistent redox and structural profiles that can compromise reproducibility in sensitive applications. Recombinant albumin eliminates these liabilities at the source.

Study Design

A model cytokine was formulated in defined buffer at 10 µg/mL and 100 µg/mL under three conditions: no albumin, Optibumin 25 at 2 mg/mL, and plasma-derived HSA at 2 mg/mL. One-milliliter aliquots were stored for up to 4 weeks at 2–8°C, room temperature, and 35–40°C, with timepoints collected at 0, 1, 2, and 4 weeks.
Recovery was assessed by capillary electrophoresis on the ProteinSimple Wes platform, with monomer quantified as a percentage of the Time 0 value to track both aggregation and loss. Bioactivity was assessed in a cytokine-responsive cell proliferation assay on samples stored for 4 weeks, benchmarked against a fresh control. Dose-response curves were fit using a 4-parameter logistic model, and EC50 was used to assess cytokine activity, with lower EC50 values indicating higher bioactivity. Comparisons were made across storage conditions and formulations.

Results

Cytokine Recovery During Storage

At 10 µg/mL, cytokine monomer recovery declined rapidly in no-albumin controls over the 4-week study, with the steepest losses observed at room temperature. Both Optibumin 25 and plasma-derived HSA preserved recovery substantially across all storage conditions. The stabilizing effect was strongest at room temperature, where albumin-containing formulations delivered up to 50% higher recovery than no-albumin controls. At 2–8°C, albumin-containing formulations delivered approximately 20% higher recovery. Optibumin 25 tracked closely with plasma-derived HSA across all timepoints and temperatures.

Loss of Recovery Drives Loss of Bioactivity

Bioactivity measurements after 4 weeks of storage mirrored the recovery data. Dose-response curves for no-albumin samples showed a clear rightward shift in EC50, indicating reduced potency — approximately 2× loss at 4°C and approximately 4× loss at room temperature. Samples containing Optibumin 25 maintained EC50 values comparable to fresh controls and to plasma-derived HSA, confirming that the recovery preserved by albumin translates directly into preserved functional activity.

Conclusion

Stabilizing dilute cytokine formulations with recombinant albumin supports more consistent performance, reduces variability during handling, and improves the robustness of cell therapy and biomanufacturing workflows. Optibumin 25 delivers these outcomes while matching the performance of plasma-derived HSA — without donor variability, viral contamination risk, or inconsistent redox profiles. For workflows where cytokine bioactivity drives downstream cell expansion, differentiation, or product potency, recombinant albumin is a direct-replacement carrier protein that removes a significant source of variability at the source.

Download the Poster

Download the full poster presentation: Enabling Room-Temperature Handling of Dilute Cytokines: Recombinant Albumin Preserves Recovery and Bioactivity.

Talk to an InVitria scientist about incorporating Optibumin 25 into your cytokine stabilization, cell culture, or biologics formulation workflow.