Graphene field-effect transistors (GFETs) can detect harmful genes through DNA hybridization, which occurs when a ‘probe DNA’ combines, or hybridizes, with its complementary ‘target DNA.’
Transistor-based biosensors are promising tools for detecting specific genes because they are cheaper, easier to operate and more sensitive than conventional sensors. Research groups are investigating how to improve fabrication methods to further bring down costs and boost output, while maintaining high sensitivity. For example, researchers in India and Japan have developed an improved method for making graphene-based transistors to detect disease-causing genes, according to a study published in the journal Science and Technology of Advanced Materials (STAM).
Graphene field-effect transistors (GFETs) can detect harmful genes through DNA hybridization, which occurs when a ‘probe DNA’ combines, or hybridizes, with its complementary ‘target DNA.’ Electrical conduction changes in the transistor when hybridization occurs. Nobutaka Hanagata of Japan’s National Institute for Materials Science and colleagues improved the sensors by attaching the probe DNA to the transistor through a simple drying process.
They deposited the DNA probe in a saline solution onto a one-atom-thick layer of graphene and left it to dry. They found the probes were successfully immobilized on the GFET surface. This eliminated the need for a costly and time-consuming addition of ‘linker’ nucleotide sequences, which have been commonly used to attach probes to transistors. In another STAM study, Korean researchers reported improving ‘dual-gate field-effect transistor’ (DG FET) biosensors by using silicon nanowires on their surface. Similar to the graphene-based transistors, when molecules bind on a field-effect transistor, a change happens in the surface’s electric charge. DG FETs are particularly good candidates as biosensors because they amplify the signal several times. Field-effect transistors using silicon nanowires have high sensitivity and selectivity, but are difficult to manufacture.
The size and position of silicon nanowires fabricated by means of chemical vapour deposition cannot always be perfectly controlled. Drawing nanorods onto a surface using an electron or ion beam allows better control of size and shape; but these methods are expensive and limited by low throughput. Won-Ju Cho of Kwangwoon University and colleagues fabricated silicon nanowires using nanoimprint lithography. In this method, a thin layer of silicon was placed on top of a substrate. This layer was then pressed using a nanoimprinter, which imprints nanosized wire-shaped lines into the surface. The areas between separate lines were then removed using a method called dry etching, which involves bombarding the material with chlorine ions. The resultant silicon nanowires were then added to a DG FET. The team found that their device was more stable and sensitive than conventional DG FETs. Both groups plan to continue refining their respective biosensors to enhance detection of genetic diseases and other applications.
Further information
Professor Nobutaka Hanagata
| E-mail: [email protected]
Nanotechnology Innovation Station
National Institute for Materials Science
Professor Won-Ju Cho
E-mail: [email protected]
Department of Electronic Materials Engineering
Kwangwoon University
Mikiko Tanifuji
| E-mail: [email protected]
Science and Technology of Advanced Materials
National Institute for Materials Science
