What is Recombinant Human Transferrin?

Why is transferrin essential in serum-free medium?

Iron is essential for haem biosynthesis, electron transport chain function (iron-sulfur clusters in Complex I, II, III), ribonucleotide reductase activity (DNA synthesis), and numerous other metabolic processes. In standard serum-containing medium, transferrin in FBS or human serum continuously delivers iron to cells. In serum-free medium, this delivery mechanism is absent — cells rapidly deplete the small intracellular iron stores and enter iron deficiency within 1–3 passages.

Why recombinant vs bovine transferrin?

Bovine transferrin extracted from bovine serum is commonly used in serum-free media but is animal-derived — incompatible with xeno-free and ACF protocols for ATMP manufacturing. OsrhTF (rice-expressed recombinant human transferrin) is identical in function to native human transferrin, animal-free, and produced under defined conditions with high lot-to-lot consistency. For clinical-grade cell manufacturing, rHSA + OsrhTF replaces the albumin and iron delivery functions of FBS in a fully defined, animal-free format.

OsrhTF in serum-free medium formulation

Add OsrhTF at 5–10 µg/mL to serum-free basal medium alongside rHSA (1–5 g/L), recombinant insulin (10 µg/mL), sodium selenite (5 ng/mL), and cell-type specific growth factors. This provides the minimal complement of FBS carrier and iron delivery functions in a defined, animal-free format.

Key Facts

• Transferrin is a ~79 kDa iron-binding glycoprotein — the primary iron carrier in blood and serum
• Cells take up iron by binding diferric transferrin (Tf-Fe2) to transferrin receptor 1 (TfR1) → receptor-mediated endocytosis → iron released in endosome → apo-transferrin recycled to cell surface
• Without transferrin in serum-free medium, cells become iron-limited within 48–72 hours → reduced proliferation → mitochondrial dysfunction → apoptosis
• Iron starvation is the most commonly overlooked cause of failed serum-free adaptation
• OsrhTF (rice-expressed recombinant human transferrin) is animal-free, xeno-free, ≥99% purity
• Standard concentration in serum-free medium: 5–10 µg/mL
• Used in: serum-free AAV production media, iPSC maintenance, MSC expansion, cultured meat satellite cell culture, any xeno-free or ACF protocol
• SeamlessBio supplies OsrhTF (Oryza sativa-expressed recombinant human transferrin)

Further Reading

• What is rHSA?
• What is Xeno-Free Cell Culture?
• Serum-Free Adaptation — Why It Fails
• rHSA vs BSA Comparison

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