<Graphene
Graphene has a frame work similar to chicken-mesh which gives electrons significant speed boosts compared to silicon circuits, and makes it mechanically stronger and stiffer than diamond. Graphene is made of sheets of single carbon atoms and finds a variety of applications in biomedical field, but the interaction between graphene and DNA, the building block of all living things has not been studied well.
Graphene DNA structure
Researchers of Pacific Northwest National Laboratory, PNNL and Princeton University have built nanostructures of graphene and DNA and tracked the interaction by attaching a fluorescent molecule to the DNA. They found that single-stranded DNA had a stronger interaction with graphene than the double stranded one. This was evident when the fluorescence dimmed significantly when single-stranded DNA rested on graphene, but double-stranded DNA only darkened slightly.
The researchers then conducted experiments to detect the difference in fluorescence and binding. When complementary DNA was added to single-stranded DNA-graphene structures, the fluorescence glowed anew indicating that the two DNAs intertwined and left the graphene surface as a new molecule.
DNA-graphene for biosensor
DNA-graphene can find applications in medicine, food safety and biodefense. The ability of DNA to turn its fluorescent light switch on and off in the proximity of graphene could be used to create a biosensor. DNA-graphene biosensor can be used for diagnosing diseases like cancer, detecting toxins in tainted food and detecting pathogens from biological weapons.
Other tests also revealed that Single-stranded DNA attached to graphene can not be easily degraded by enzymes and the structures remain stable, which phenomena could lead to drug delivery for gene therapy.
A graphene-DNA biosensor would detect diseases by fishing for molecules involved in disease. Like stringing a worm on a hook, scientists would place DNA from a gene that's known to contribute to a disease's development onto a piece of graphene. The researchers would then dip the biosensor hook into treated blood, saliva or another bodily fluid. If DNA from the disease-causing gene is in the fluid and takes the bait, the biosensor gives off a signal that scientists can detect.
Graphene oxide attaches fluorescent dye
Researchers of National University of Singapore have found that a specially designed fluorescent dye called PNPB, a water soluble and positively charged dye, namely, 4-(1-pyrenylvinyl)- N-butylpyridinium bromide can attach to and stack parallel to graphene oxide. The interactions between these two compounds create a charge-transfer complex that quenches the PNPB dye’s fluorescence, leading to new applications in both biological sensing and optical safety. A simple ion exchange strategy for electrostatic complexation of graphene oxide with a synthetic dye forms an energy- or charge-transfer complex and exhibits enhanced properties for biosensing and optical limiting. This positively charged dye can interact with negatively charged graphene oxide to form a fluorescence-quenched charge-transfer complex. The fluorescence of PNPB is switched on or off depending on whether it complexes more strongly with graphene oxide or other biomolecules.
DNA motion through graphene
Researchers in the Netherlands fed individual strands of DNA through nanometre-sized holes and have proved the principle of a revolutionary new DNA sequencing technique. The breakthrough is part of a worldwide race to develop fast and low-cost strategies to analyse these codes that underpin the chemistry of life.
Researchers at the Kavli Institute of Nanoscience have demonstrated DNA motion through graphene. They created a series of pores ranging from 5 to 25 nm in diameter by placing flakes of graphene over a silicon nitride membrane and drilling nanosized holes in the graphene using an electron beam. By applying a voltage of 200 mV across the graphene membrane, a series of spikes were observed in an electric current that scales the gap which correspond to drops in conductance when DNA strands slide across the gap via a biochemical process known as translocation.