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Nanoparticles detect cocaine

A new fast and portable method to detect minute quantities of cocaine and other small molecules using gold nanoparticles and DNA "aptamers" has been developed by researchers in China and Singapore. The technique is based on the characteristic colour change of the gold nanoparticles and aptamers from red to blue when cocaine is present.%XC9ns/{e(dk)nN
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[url=http://nanotechweb.org/cws/article/tech/35903/1/080942-1][img]http://images.iop.org/objects/nano/news/thumb/7/9/42/080942-1.jpg[/img]
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Aptamers are artificial nucleic-acid receptors that have a high affinity for certain ligands. In this work, Chunhai Fan of the Shanghai Institute of Applied Physics and colleagues made an aptamer consisting of two pieces of random, coil-like single-stranded DNA that has a high affinity for cocaine molecules.
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8Wu9j$oP When cocaine binds to the aptamer, it alters the affinity between the aptamer and gold nanoparticles, which in turn affects the stability of the gold nanoparticles in salt solution, explains Fan. In the absence of cocaine, the aptamer is attached to the gold nanoparticles. The aptamer–nanoparticles complex is stable and red in colour. When there is cocaine present, it binds to the aptamer, so liberating the aptamer from the nanoparticles. This leads to the aggregation of nanoparticles in solution, turning it blue. ^Ze%Y1R1Z
[url=http://nanotechweb.org/cws/article/tech/35903/1/080942-2][img]http://images.iop.org/objects/nano/news/thumb/7/9/42/080942-2.jpg[/img]
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"U e7A @7gz2w The technique works well at room temperature and can detect micromolar quantities of cocaine in a matter of minutes. It could also be extended to detect other targets using different types of aptamers. Indeed, Fan's team has already successfully detected adenosine and potassium in solution using anti-adenosine and "G-quartet" aptamers.
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Currently, the method only works in the laboratory and with relatively pure solutions. "We are trying to develop a more selective approach that can work perfectly in highly complicated environments such as blood serum," Fan told [i]nanotechweb.org[/i].
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DxEw\2},n1g The researchers reported their work in [i]Small[/i].