Graphene DNA Sequencing

Researchers at the University of Illinois at Urbana-Champaign have found that crumpling graphene makes it more than ten thousand times more sensitive to DNA by creating electrical "hot spots". This discovery could assist in addressing a known issue of graphene-based biosensors - the face that they require a lot of DNA in order to function properly.

"This sensor can detect ultra-low concentrations of molecules that are markers of disease, which is important for early diagnosis," said study leader Rashid Bashir, a professor of bioengineering and the dean of the Grainger College of Engineering at Illinois. "It's very sensitive, it's low-cost, it's easy to use, and it's using graphene in a new way."

Cardea Bio (formerly: Nanomedical Diagnostics) and Nanosens Innovations have joined forces to accelerate the development of the Genome Sensor: the world's first DNA search engine that runs on CRISPR-Chip technology.

Cardea has announced the finalization of their merger-acquisition of Nanosens Innovations, the creators of CRISPR-Chip. Cardea first came out with the news of the proposed merger in September, along with the announcement of their Early Access Program for the Genome Sensor. Built with CRISPR-Chip technology, the Genome Sensor is the world’s first DNA search engine. It can google genomes to detect genetic mutations and variations.

Researchers at the University of Illinois examined how tiny defects in graphene membranes, formed during fabrication, could be used to improve molecule transport. They found that the defects make a big difference in how molecules move along a membrane surface. Instead of trying to fix these flaws, the team set out to use them to help direct molecules into the membrane pores.

Nanopore membranes have generated interest in biomedical research because they help researchers investigate individual molecules - atom by atom - by pulling them through pores for physical and chemical characterization. This technology could ultimately lead to devices that can quickly sequence DNA, RNA or proteins.

Scientists have noticed many years ago that when buckyballs (soccer ball shaped carbon molecules) are thrown onto a certain type of multilayer graphene, they spontaneously assemble into single-file chains that stretched across the graphene surface. Now, researchers from Brown University have explained how the phenomenon works, and that explanation could pave the way for a new type of controlled molecular self-assembly.

BUCKYBALLS LINED UP ON A LAYERED GRAPHENE SURFACE

The Brown team shows that tiny, electrically charged crinkles in graphene sheets can interact with molecules on the surface, arranging those molecules in electric fields along the paths of the crinkles.

Researchers at the University of Illinois at Urbana-Champaign have developed new theories regarding the compression of water under a high-gradient electric field. They found that a high electric field applied to a tiny hole in a graphene membrane would compress the water molecules travelling through the pore by 3%. The predicted water compression may eventually prove useful in high-precision filtering of biomolecules for biomedical research.

The team commented: "This is an unexpected phenomenon, contrary to what we thought we knew about nanopore transport. It took three years to work out what it was the simulations were showing us. After exploring many potential solutions, the breakthrough came when we realized that we should not assume water is incompressible. Now that we understand what's happening in the computer simulations, we are able to reproduce this phenomenon in theoretical calculations."

Researchers from Brown University have discovered yet another peculiar and potentially useful property of graphene, that could be useful in guiding nanoscale self-assembly or in analyzing DNA or other biomolecules.

Their new study demonstrates mathematically what happens to stacks of graphene sheets under slight lateral compression—a gentle squeeze from their sides. Rather than forming smooth, gently sloping warps and wrinkles across the surface, the researchers found that layered graphene forms sharp, saw-tooth ridges that turn apparently have interesting electrical properties.

University of Arkansas researchers are working together, with support from the National Institutes of Health, to make that prospect of graphene-based sensors that sequence a patient's genome to predict diseases more realistic. Steve Tung, professor of mechanical engineering, and Jin-Woo Kim, professor of biological engineering, have received a grant (of approximately $400,000) from the NIH's Human Genome Research Institute to develop nanoscale technology designed to make DNA sequencing faster, cheaper and easier.

The base of the research builds on the concept of nanochannel measurement, in which individual strands of DNA pass through a tiny channel. The passage of those strands interrupts an electrical current and a sensor detects the nature of the interruption, telling scientists which nucleotide has passed through the channel.

Researchers at the University of Pennsylvania have used graphene to increase the sensitivity of diagnostic devices, in particular those used to monitor and treat HIV. The team combined a trick of DNA engineering which involves an engineered piece of DNA called a hairpin, with biosensors, increasing the sensitivity of the sensors by a factor of 50,000 in less than an hour.

The biosensorsare made with graphene, and so can be used as an extremely sensitive way of detecting biological signals, measuring the current that flows through graphene surface in the presence of biomolecules. When DNA or RNA molecules bind to the graphene, it produces a big change in the conductivity of the atomically thin material, allowing the researchers to detect infections and to measure viral loads.

As part of a national research collaboration, Spanish researchers including the ICN2 have reached a milestone in graphene research, that potentially brings science a step closer to using graphene in filtration and sensing applications.

The researchers have successfully synthesized a graphene membrane with pores whose size, shape and density can be tuned with atomic precision at the nanoscale. Engineering pores at the nanoscale in graphene can change its fundamental properties. It becomes permeable or sieve-like, and this change alone, combined with graphene's intrinsic strength and small dimensions, points to its future use as the most resilient, energy-efficient and selective filter for extremely small substances including greenhouse gases, salts and biomolecules.

Researchers at Leiden University in the Netherlands have managed to bring two graphene layers so close together that an electric current spontaneously jumps across. This could enable scientists to study the edges of graphene and use them for sequencing DNA with a precision beyond existing technologies.

The team tilted two one-atom-thick sheets of graphene so that they only meet in one point, where electrons jump across from one layer to the other. Previous attempts with graphene electrodes failed because the layers are 'floppy' by nature. The Leiden scientists deposited them on a silicon substrate, making them rigid all the way to the edge. They brought both layers close enough together so that tunneling occurs—a quantum mechanical phenomenon where electrons spontaneously jump to a neighboring material, even though there is no direct contact. Any small object in between will enhance the tunneling. The number of electrons tunneling through will tell researchers about some of its properties.