What is rHSA (Recombinant Human Serum Albumin)?

Why use rHSA instead of BSA?

Bovine serum albumin (BSA) is widely used as an albumin source in serum-free media but has two limitations: it is animal-derived (problematic for xeno-free ATMP manufacturing) and its drug binding affinity differs from human albumin for many compounds (relevant for DMPK protein binding assays). rHSA solves both problems — animal-free production with human-sequence binding properties.

rHSA in serum-free medium formulation

In a complete serum-free medium replacing FBS, rHSA at 1–5 g/L provides the carrier protein function. It must be combined with other FBS replacement components: recombinant transferrin (OsrhTF, for iron delivery), recombinant insulin (for glucose uptake signalling), recombinant IGF-1, EGF or FGF-2 (cell-type specific growth factors), and selenium (antioxidant). Without rHSA, lipid-soluble nutrients cannot be delivered to cells in aqueous medium.

rHSA variants from SeamlessBio

SeamlessBio supplies three rHSA grades: Economy (cost-effective for non-GMP research), Premium (higher purity for sensitive applications), and CHO-expressed (mammalian expression system for specific glycosylation requirements).

Key Facts

• rHSA has identical sequence to native HSA (585 amino acids, MW ~66.5 kDa) — same drug binding sites (Site I warfarin site, Site II diazepam site)
• Produced in rice (OsrhHSA) or yeast — completely animal-free and xeno-free
• Primary functions in serum-free medium: fatty acid carrier, ROS scavenger, drug/hormone solubiliser, osmotic contributor
• Used at 1–5 g/L in serum-free cell culture medium to replace albumin function of FBS
• Critical component in serum-free AAV production media — stabilises viral particles during harvest and purification
• For DMPK fu,plasma assays: rHSA gives human-relevant drug binding constants (BSA differs from HSA for many acidic drugs)
• GMP-grade available with full manufacturing documentation for ATMP and clinical manufacturing
• SeamlessBio supplies OsrhHSA (rice-expressed, ≥95% purity) in Economy, Premium and CHO-expressed variants

Further Reading

• rHSA vs BSA — Which Should You Use?
• What is Xeno-Free Cell Culture?
• Serum-Free Adaptation Protocol
• What is Recombinant Transferrin?

SeamlessBio GmbH · Passau, Germany · info@seamlessbio.de · +49 851 37932226