Is Precipitation In FBS Normal?

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Wed, 10 Apr 2019

Is Precipitation In FBS Normal?

Is the precipitation I sometimes see in my FBS normal?

  • Yes - Some material will normally come out of solution in all serum products.
    • Fibrin
    • Calcium phosphate and other salts or “tiny black dots”
    • Fatty Ester of Cholesterol
    • Protein precipitation

  Precipitation will increase in serum due to:

  • heat inactivation
  • incubation at 37°C
  • Often leads to false conclusions
  • freeze / thaw cycles
  • not mixing during the thawing process
  • gamma irradiation
  • long term storage at 2-8°C

Precipitates do not harm cells

  • Based on extensive testing.
  • Confirmed by our customers

These precipitates occur in all serum products, including our competitors.

  • From Invitrogen’s/Thermo's website “GIBCO FBS is not pre-aged. Upon storage at 2 to 8°C, the possibility exists for various proteins and lipoproteins in serum (e.g., cold agglutinins, fibrinogen, vitronectin, etc.) to aggregate, and form either perceptible material or observed turbidity. This should not affect serum performance. We recommend that you store FBS at -20°C and avoid repeated freeze-thaw cycles.

  • From Sigma FBS Product Information Sheet:   “Turbidity or flocculent material may appear upon thawing or prolonged storage at refrigerator temperature.  This is a normal occurrence common to most serum products and is not detrimental to its performance”

  • From JRH (now Sigma) Technical Bulletin:  “Cryoprecipitates are not uncommon, even in serum that is thawed using the recommended procedure. This is normal and will not affect product performance.”  and “These cryoprecipitates are not toxic to cell cultures , but they affect the appearance and consistency of each bottle of serum.”

Why Mixing During/After Thawing is Important