Quick Definition
What is Low Endotoxin BSA?: Low endotoxin BSA is bovine serum albumin processed and tested to contain less than 1 EU/mg endotoxin. Standard BSA can contain 1–100 EU/mg from Gram-negative bacterial contamination during processing — sufficient to activate TLR4 signalling in sensitive cell types at working concentrations used in cell culture.
When does BSA endotoxin cause problems?
BSA is commonly used in assay buffers at 0.1–5% (1–50 mg/mL). At these concentrations, even BSA with "moderate" endotoxin of 10 EU/mg delivers 10–500 EU/mL into the assay — well above the TLR4 activation threshold of ~0.1 EU/mL. In any assay measuring cytokine production, NF-κB activation, or immune cell activation, this background endotoxin produces false positive results independent of the experimental treatment.
Key Facts
- Standard BSA: 1–100 EU/mg endotoxin depending on grade and supplier
- Low endotoxin BSA: <1 EU/mg — tested by LAL chromogenic assay per lot
- At 1 mg/mL BSA with standard BSA at 10 EU/mg = 10 EU/mL in medium — above the TLR4 activation threshold
- TLR4 activation at >0.1 EU/mL triggers NF-κB → IL-6, TNF-α, IL-1β in monocytes, macrophages and hepatocytes
- Required for: cytokine ELISA calibration buffers, cell-based cytokine assays, receptor binding studies with immune cell lines
- Same functional performance as standard BSA — endotoxin removal does not affect albumin binding properties
Further Reading
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