Fetal Bovine Serum, Sterile

Put the bottle in a refrigerator at 2-8°C overnight, or in a 37°C water bath with the water kept below the cap, and swirl it gently as it thaws. Take it out as soon as the last ice has melted; never thaw above 37°C, on the bench or in a microwave. Then mix, aliquot what you will not use right away and return the aliquots to the label temperature. The full walkthrough with diagrams: how to thaw frozen serum.

Aliquots can go back to the freezer once; the bulk bottle should not. Every freeze-thaw cycle concentrates salts, shifts pH and stresses the proteins, and complement activity drops with each one. Split the bottle into single-use tubes on the first thaw so each portion is only ever thawed once, or hold the thawed bottle at 2-8°C and use it within the window on the product page. See how to thaw frozen serum.

Usually yes. Some haze or flocculent material after thawing is cryoprecipitate (fibrin, lipoprotein and calcium salts that came out of solution while frozen), and it does not change how the serum performs. Warm the bottle briefly to 37°C and swirl to redissolve most of it, or filter through a 0.45 µm filter if you need a clear product. A strong odor, a color change, or turbidity that keeps increasing at room temperature is contamination, not cryoprecipitate: do not use the bottle; contact us with the lot number. More in how to thaw frozen serum.