THE tiny gold particles used to build nanomachines could be harvested from
fields of alfalfa, a crop grown for animal feed. The plants can extract metal
ions from gold ore in a nutrient solution to make particles of pure gold.
Nanotechnologists use gold particles to link different molecules, which is
vital for making complex, miniature structures. Sulphur-containing chemical
groups called thiols are tagged to the end of each molecule and these form
strong bonds with the gold.
Usually gold is extracted from its ore by mixing it with cyanide. Removing
the gold from the resulting compound is very expensive and potentially
polluting. So Miguel Jose Yacaman at the University of Texas in El Paso has
worked out how to get plants to do the hard work, he鈥檒l report in a forthcoming
edition of the journal Nano Letters. He grew alfalfa in a nutrient solution rich
in a gold ore. Sure enough, the plants extracted gold ions from the ore,
converting it to pure gold. When he inspected the roots and stems of the plants
with an electron microscope, he found they contained gold particles measuring 4
nanometres across. Yacaman says that plants could one day be used as factories
to produce nanoparticles. 鈥淭he same way we use animals to produce vaccines,鈥� he
says.
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Mark Welland, who heads the Interdisciplinary Research Collaboration in
Nanotechnology at the University of Cambridge, says scientists are unlikely to
switch to plant-grown nanoparticles just yet. 鈥淏ut if you have metal
contamination in soil, it鈥檚 useful if you can just grow plants to remove it and
produce nanoparticles at the same time,鈥� he says. Yacaman is now doing tests to
see if plants can also produce radioactive nanoparticles. If so, the particles
could be ideal for irradiating tumours, he says.