The world of nanomedicine has recently moved one step closer to helping cure some of the most intractable diseases and conditions. Researchers from India and South Korea have synthesized a graphene-based, gold-nanoparticle-covered sensor that is capable of detecting minute traces of DNA. The device paves the way for improving the detection of DNA sequences linked to various genetic diseases.
In order to detect DNA a sensor must somehow discriminate between the four bases of DNA, each of which exist with a signature oxidation potential. Previous sensors based on glassy carbon or carbon nanotubes do not have this capability, however, graphene, with its unique structure and electrical properties, is an excellent alternative.
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 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 DNA sequence worked as a probe to capture target DNA, showing a change in resistance and current after interacting with the target.
“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 original 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.
Jayakumar, K. et al. Gold nanoparticle decorated graphene core first generation PAMAM dendrimer for label free electrochemical DNA hybridization sensing. Biosens. Bioelectron. 31, 406-412 (2012)