Graphene-based DNA sensor
doi:10.1038/nindia.2012.15 Published online 31 January 2012
Researchers have synthesized a graphene-based, gold-nanoparticle-covered sensor capable of detecting minute traces of DNA. This device could be a useful diagnostic tool for detecting DNA sequences linked to various genetic diseases.
To detect DNA, a sensor must be able to discriminate between the four bases of DNA at different oxidation potentials. Sensors based on glassy carbon or carbon nanotubes do not have this capability. Graphene is a good alternative with unique structure and electrical properties. However, fabricating existing graphene-based sensors requires the use of expensive chemical vapour deposition and lithographic techniques.
To devise a cost-effective technique for fabricating graphene-based DNA sensors, the researchers synthesized a composite single layer from graphene and polyamidoamine dendrimer, a synthetic polymer. They dipped the composite in mercaptopropionic acid and deposited it on a gold electrode. They decorated the sensor's surface with gold nanoparticles. Finally, they deposited a modified synthetic DNA sequence that codes for cytokeratin 20, a protein linked to various tumour diseases, on top of the gold nanoparticles.
The DNA sequence worked as a probe to capture target DNA, showing a change in resistance and current after interacting with the target.
The sensor was able to discriminate between complimentary double-stranded DNA, non-complimentary single-stranded DNA and single-nucleotide polymorphism surfaces. A single-nucleotide polymorphism is a single-base mismatch that causes most genetic diseases. The sensor was 1,000 times more sensitive than those without a graphene core. This remarkable enhancement in sensitivity is due not only to the graphene core, but also the gold nanoparticles, which provided a large capture probe density.
"The sensor showed high selectivity and sensitivity at nanomolar concentrations, with the lowest detection limit being ten times lower than for a sensor without graphene," says lead researcher V. Dharuman.
The authors of this work are from: Department of Bioelectronics and Biosensors, and Department of Biotechnology, Alagappa University, Karaikudi, and Department of Chemistry, Pondicherry University, Pondicherry, India, and Laboratory for Advanced Biotechnology and Biomedical micro Instrumentation, Biotech Centre, Department of Chemistry, Pohang University of Science and Technology, Hyojadong, Pohang, South Korea.