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Researchers in Japan have shown that they can remove Escherichia coli from drinking water using tiny tubes made of human serum albumin.

E. coli is a very common type of bacteria, many strains of which are harmless. Some strains, however, such as enterohemorrhagic E. coli O157, are life-threatening to humans. This is particularly problematic in the developing world, where fruit and vegetables washed in contaminated water can cause severe food-poisoning and even death.

The elegant method, devised by Teruyuki Komatsu and co-workers at Chuo University, Tokyo, begins by depositing microtubes made from alternating layers of human serum albumin (HSA) and poly-L-arginine onto a polycarbonate template. The template is then dissolved away to leave a hollow tube, which is just the right size to fit the E. coli bacterium. Key to removing E. coli from a solution is its strong binding affinity for HSA, which attracts the bacteria into the tube. So effective is this binding, that just 1.5μg of microtubes, added to a liter of contaminated water containing 100,000 bacteria were able to remove the bacteria with almost 100% efficiency. The final touch is the incorporation of a layer of magnetite (iron (II) oxide) nanoparticles into the microtubes to allow their easy removal from the solution using a magnetic field.

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