If you鈥檝e ever dropped your mobile phone in dishwater, you can now claim you were testing the water for bacterial contamination. It seems liquid crystals, ubiquitous in electronic displays, are the best way to detect water-borne toxins.
When suspended in water, the molecules in a liquid crystal droplet normally form chains that wrap around the droplet like the lines of longitude on a globe. But in the presence of endotoxins, disease-causing molecules produced by Escherichia coli bacteria, they rearrange to form a pattern that radiates from the drop鈥檚 centre.
Previously, coating a droplet鈥檚 entire surface with toxins was thought to be necessary to produce the change, called an 鈥渙rdering transition鈥�.
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Now at the University of Wisconsin-Madison and colleagues have shown that only the 鈥減oles鈥� of the droplet, where the longitudinal chains of its molecules meet up, need to contact the toxins to produce the realignment.
That suggests liquid crystals can detect endotoxins at concentrations 10 times as low as currently possible, Abbott says. 鈥淭he surprise was that we could trigger this ordering transition with such a small number of molecules,鈥� says Abbott.
鈥淚t鈥檚 a wonderful piece of work,鈥� says at Kent State University in Ohio, who was not involved in the research. 鈥淚n order to trigger the ordering transition, one needs a much smaller amount of stimuli than one might normally think.鈥�
Liquid crystal droplets could one day help ensure the safety of saline and other injectable medical fluids.
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