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Endotoxins
Endotoxins
What is an endotoxin?
- Found in the outer membrane of Gram-negative bacteria like E. coli.
- They’re heat-stable and not destroyed by typical sterilization like autoclaving.
- Even tiny amounts can trigger fever, inflammation, or endotoxin shock in animals or humans.
Why test peptides for endotoxins?
- During peptide synthesis, handling, or lyophilization, bacterial contamination can occur.
- For research peptides, endotoxin testing ensures the material is free from these toxic residues, especially if used in in vivo research models.
- Regulatory labs (like 503B pharmacies) have strict limits—often < 0.25 EU/mL for injectable solutions.
Testing methods
- LAL Assay (Limulus Amebocyte Lysate)
- Uses enzymes from horseshoe crab blood that clot in the presence of endotoxins.
- Can be gel-clot, turbidimetric, or chromogenic (color-change) formats.
- Most common in both research and pharmaceutical testing.
- Recombinant Factor C (rFC) Assay
- Synthetic alternative to LAL—no animal harvesting.
- Fluorescent readout; same sensitivity.
Result format
- Reported in Endotoxin Units (EU) per milliliter or per milligram of sample.
- Example: “< 0.05 EU/mg” means the peptide meets extremely low endotoxin limits.