Scientists in China have developed a simple sensor for proteins in DNA using gold nanoparticles.

The detection is based on the gold nanoparticles changing colour, which can be seen readily with the naked eye, explained Shaojun Dong, leader of the team at the Chinese Academy of Sciences, Changchun, China. When the gold nanoparticles interact with single stranded DNA (ssDNA), they are dispersed in solution and give out a red colour. When the ssDNA is bound to a protein, it does not interact with the nanoparticles and as a result they give out a blue colour.

The technique uses a new class of single stranded DNA/RNA molecules called aptamers. Aptamers have high recognition ability to specific molecular targets such as proteins or cells. Recently, a variety of aptamer-based methods has been developed for molecular recognition and detection, Dong explained; however, these are based on thiol-gold chemistry, which requires modification of the gold nanoparticles. 'Our method avoids the need for modifying gold nanoparticles, and thus provides a simple, sensitive and cost-effective approach for molecular recognition', he said.

Dong sees many opportunities for future development of the sensor. 'It could be extended to not only other aptamers but also DNAzymes,' he said, 'and what's more, the probe itself could be replaced by silver nanoparticles.' Dong also thinks that the technique could also be used for ssDNA structure detection instead of the traditional fluorescence sensors.

Sarah Dixon