Researchers reveal how surfactant samples may mask dangerous endotoxins during LAL testing

New work suggests that in such formulations endotoxin can remain undetected by Limulus amebocyte lysate (LAL) detection systems due to low endotoxin recovery (LER)

A new paper has been published that suggests commonly used excipients are capable of masking hazardous amounts of endotoxin

Endotoxins are lipopolysaccharides produced by Gram-negative bacteria during bacterial cell division, lysis and at cell death.

Part of the lipopolysaccharide is highly toxic to humans and when in contact with blood can trigger a severe reactions such as fever or septic shock.

Bacterial endotoxin testing of drug products for parenteral administration is therefore mandatory.

Over the past few decades Limulus amebocyte (LAL) lysate (obtained from the horseshoe crab) has been the most sensitive method for the detection of endotoxins and is well accepted in a broad field of applications.

However, recently, low endotoxin recovery (LER) in biopharmaceutical drug products has been noticed, whereby the detection of potential endotoxin contaminations is not ensured.

Notably, many of these drug products contain surfactants, which can have crucial effects on the detectability of endotoxin.

Researchers, J. Reich and H. Motschmann, Institute of Physical and Theoretical Chemistry, University of Regensburg, Germany, Pierre Lang , F. Hoffmann-La Roche, Switzerland, and H. Graller, Hyglos, Bernried, Germany, set out to discover what is behind the LER phenomenon.

To analyse the mechanisms behind LER, the researchers investigated endotoxin detection in samples containing nonionic surfactants in various buffer systems.

The results, published in the paper online 25 July 2016, show that the process of LER is kinetically controlled and temperature-dependent.

Furthermore, only the simultaneous presence of nonionic surfactants and components capable of forming metal complexes resulted in LER.

Following their research they believe that the LER phenomenon is caused by endotoxin masking and not by test interference.

The experiments showed that hazardous amounts of endotoxin can remain undetectable within such formulations.

They conclude that 'the supramolecular structure of endotoxin is altered and exhibits only a limited susceptibility in binding to the Factor C of Limulus-based detection systems.'

The paper states: 'Currently, it is not known whether masked endotoxin activates the innate immune system. But bacterial endotoxin testing should be performed with care, especially in the presence of surfactants and chelators.'

The paper Masking of endotoxin in surfactant samples: Effects on Limulus-based detection systems, Biologicals (2016) is available online at

For further reading about endotoxin testing see: