Charcoal-Treated Serum (CTS)
Inactivate fetal bovine serum (FBS) by incubating for 30 min at 56°C. To remove endogenous thyroid hormones in FBS, add 6.5 g of activated charcoal (powder, neutral) to FBS and stir gently overnight at 4°C with a stir bar (Yoshizato et al. 1980). Centrifuge FBS at 10,000 rpm for 1 h at 4°C in a benchtop centrifuge twice, filter sterilize the supernatant through a 0.22-µm filter, and store at −20°C.
