How to choose batches of FBS for cell culture with significant differences in pH and color between recent batches?

If HepG2 and 293T are sensitive to serum, it is recommended to sign a lot number lock agreement with the primary distributor, specifying that returns or exchanges are allowed if the COA does not match or cell validation fails. Ask the supplier to send small samples from two candidate lot numbers, and after selection, sign for whole-batch procurement. The contract should clearly state the same place of origin, the same catalog number, and delivery time. Endotoxin, hemoglobin, and total protein can only be used for preliminary screening; the final judgment should be based on your own cell attachment and proliferation data. Do not accept bulk goods of unknown origin, near expiration, or at abnormally low prices; the money saved is often eaten up by experimental variability.

Color depth and pH fluctuations do not necessarily indicate deterioration, as blood collection, filtration, storage, and repeated freeze-thaw cycles may all affect it. After opening the bottle, it should be divided into smaller packages to reduce freezing and thawing. When selecting batches, the pH and osmotic pressure of the same batch of goods should be measured first, and a small sample should be left for cell testing to confirm that the cells adhere to the wall normally before opening the large bottle. Before hoarding, you need to confirm with the sales team that the entire batch of inventory can be locked by you, and avoid the situation of 'testing batch A and receiving batch B', which is more crucial than looking at COA.

It is best to first order small samples of 2-3 candidate lot numbers, 50-100 mL each, and simultaneously revive HepG2 and 293T cells, using a fixed seeding density for 3 consecutive passages, recording attachment time, viability, and doubling time. Large differences in color and pH do not necessarily mean the lot is unusable, but if performing transfection or viral packaging, lot-to-lot consistency is critical. After the small-sample validation passes, stock up according to annual usage and require the supplier to specify the lot number on the order; otherwise, the next delivery may be a different lot.

Don't just look at the COA on the official website when purchasing, ask the supplier to provide scanned copies of the COA for the actual batch received. Our focus is on card toxins ≤ 10 EU/mL, and primary or immune related drugs will require ≤ 5 EU/mL; Hemoglobin is generally required to be ≤ 20 mg/dL, and dark color is often related to red breakdown; The total protein is usually in the range of 3.5-5.5 g/dL, but different brands have different units, and the key is not to fluctuate too much between batches. The pH is usually between 7.0-7.4 when it leaves the factory, and it should be tested again after arrival. When selecting batch numbers, sales personnel are required to lock in inventory of the same batch number to avoid changing batches midway.