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.
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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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