Store unopened Fetal Bovine Serum (FBS) long-term at -10℃ to -30℃ in a dedicated manual-defrost freezer (never auto-defrost). Once thawed, immediately divide the serum into single-use aliquots to prevent repeat freeze-thaw cycles, and keep them protected from light. Store active liquid aliquots at 2℃ to 8℃ and use them within 2 to 4 weeks.
⚠️ Key Storage Hazards
1.Avoid Auto-Defrost Freezers: Frost-free freezers heat up periodically to melt ice, causing micro-thaw cycles that degrade growth factors and create heavy precipitation.
2.Prevent Protein Shearing: Repeated freeze-thawing forces ice crystals to reform, breaking down protein structures and causing irreversible aggregation.
3.Shield from Light: Ambient light destroys photo-sensitive vitamins (e.g., riboflavin) and oxidizes serum lipids over time.
⚠️ 4-Step Storage Protocol
1. Deep Freezing (Manual Defrost):-10°C to -30°C.
Place unopened bottles directly into a manual-defrost freezer upon arrival, keeping them boxed to block light exposure.
2. Thaw & Mix Thoroughly:Post-Thaw.Thaw gradually (2℃–8℃ overnight, then 37℃ bath with swirling) to ensure a homogeneous solution before opening.
3. Aseptic Aliquoting:Laminar Flow Hood.
Divide thawed serum into pre-sterilized, single-use working volumes (e.g., 10mL or 50mL tubes) to eliminate repeat freezing.
4.Refreeze & Label:Dark Storage.
Immediately return working aliquots to -20℃. Keep active liquid tubes at 2℃ –8℃ for no longer than 4 weeks.
⚠️ Temperature Comparison
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Storage Condition
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Temp Range
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Max Shelf Life
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Impact on Quality
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Manual Defrost Deep Freezer
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-10℃ to -30℃
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2~5 Years
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Gold Standard: Fully preserves protein activity.
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Refrigerator(Liquid)
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2℃ to 8℃
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2~4 Weeks
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Short-Term: Gradual activity loss after 30 days.
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❓ Frequently Asked Questions
Q: How long does unopened FBS last at -20℃
A: Unopened FBS stored in a manual-defrost freezer at -20℃ or colder remains stable for up to 5 years from the manufacturing date.
Q: Can I refreeze leftover liquid serum from the fridge?
A: Refreezing liquid serum kept at 2℃ to 8℃ for an extended period is not recommended, as it causes heavy protein precipitation and degrades cell growth performance.
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