Unlike live bacterial contamination, endotoxins are not removed by sterile filtration and do not go away when the bacteria die: they are heat-resistant molecules that stay in the material. That is why a product can be sterile and still contain endotoxins.
They are measured with the LAL test (Limulus amebocyte lysate), based on how horseshoe crab blood reacts to these molecules, or with recombinant alternatives. The result is expressed in endotoxin units (EU) per milligram or per millilitre.
In research, their relevance depends on the experiment: in cell cultures or animal models, endotoxins can activate the immune system and produce results wrongly attributed to the peptide being studied, especially in studies on inflammation or immunity.
If a study measures inflammation or immune response, it is worth knowing whether the material was tested for endotoxins. It is one of the classic causes of results that later fail to replicate.
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Definition for educational and scientific purposes. It is not medical advice or a recommendation for use. NeoPeptidos products are sold labelled for research use only (RUO).