Safe Jabs Thanks to Horseshoe Crabs: Making Sure Your Injection is Free of Endotoxins

Allen Burgenson, Lonza’s expert for all things testing, speaks to us about the dangers of endotoxin contamination and the future of non-animal testing for it.

“Before testing for endotoxins in the 1940s, a physician literally had to gauge the risk to your life because of something called injection fever,” explains Allen Burgenson. Luckily, we’ve come a long way since then. Thanks to advanced testing methods, one can rest assured today that any sort of injection or implant is completely free of dangerous endotoxins. Currently, the predominant mode is Limulus Amebocyte Lysate (LAL) testing, in which scientists harvest the bright blue blood of American Horseshoe Crabs and use the animal’s primitive immune system to look for clotting reactions that would indicate the presence of any endotoxins. The horseshoe crabs, Burgenson explains, survive the extraction unscathed and are safely returned to the waters in less than 24 hours. However, in a continual attempt to remove animals from the testing pipeline, Lonza’s recombinant factor C assay known as PyroGene could eventually replace LAL testing.

Curious to Know More?

In Episode 2 of the new season of the podcast A View On, host Martina Ribarhestericova speaks with Lonza expert Allen Burgenson to discuss his close bond with the American Horseshoe Crab and the history of testing for endotoxin contamination.


Endotoxins are parts of bacterial membranes that could lead to a harmful reaction – or even death – if they enter a patient’s bloodstream or spinal fluid. Surprisingly, we have kilograms of endotoxins in our stomachs, but even little more than a nanogram in the bloodstream could be deadly.

Bacterial endotoxin tests, or BETs, is the general name for all assays used to detect endotoxins.

Rabbit pyrogen tests are BETs that were developed in the 1940s using rabbits as test subjects. To ascertain the endotoxic danger to humans, the scientist observes a rabbit’s reaction to an injection over a period of 3 hours. The European Pharmacopoeia Commission decided in June 2021 to completely replace the rabbit pyrogen test (RPT) within approximately 5 years.

Limulus Amebocyte Lysate (LAL) is an aqueous extract of blood cells (amoebocytes) from the horseshoe crab, Limulus Polyphemus, that enables batch testing of vaccines and other drugs for endotoxins. The crab’s extracted blood is a surprising blue color due to the crabs’ copper-based Hamasyan. The obtained LAL is an opaque white-colored liquid that clots in the presence of any toxicity.

PyroGene recombinant factor C is an animal-free way to test for endotoxins. It was initially developed at the National University of Singapore by Lin Deng and her husband Bo Ho to save money on testing at their relatively small lab. Lonza collaborated with Deng and Ho to become the first company to offer the test on a commercial scale.

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