Liquid crystals can detect bacterial infections

Illustration for article titled Liquid crystals can detect bacterial infections

Liquid crystals - yes the same as the ones in your calculator — may soon save lives: they'll be detecting deadly bacterial infections. It turns out liquid crystals are incredibly sensitive to endotoxin, a lipid that's found on the outside of many bacteria, including E. coli and Salmonella.


Liquid crystal has a crystalline-like order to its structures. The endotoxin interacts with tiny defects in these structures, and changes the molecular orientation of the droplets of liquid crystal — a change big enough to be spotted by microscopes.

All it takes is a couple of picograms of endotoxin per milliliter, and the liquid crystals are precise enough to pick up the infection in less than a minute. Liquid crystal is notably more sensitive than the current test for the lipid, which relies on horseshoe crab blood. The horseshoe crab's blood combats infection by clotting around the endotoxin. Currently, scientists test for the lipid by harvesting the crabs' blood, and then releasing the enervated animals. With this new test, we'll get more accurate results and the horseshoe crabs can live more peacefully.

Images of liquid crystals via Sciencescapes


As someone who has to do regular Limulus Amebocyte Lysate (LAL) tests, the one that comes from horseshoe crab blood, I can only hope this one is easier to carry out. LAL tests are a pain. Mostly we use them to test for endotoxin contamination, rather than directly testing for bacteria. Even the LAL test is sensitive enough that even a tiny number of gram-negative bacteria is going to overwhelm it; it's the tiny amounts of endotoxin that stick to absolutely everything that are the hardest to get rid of.