Graphene and DNA sequencing: introduction and market status - Page 2

Researchers at the Institute for Basic Science (IBS) managed to observe the movement of molecules stored inside a graphene pocket without the need to stain them. This study opens the door to using graphene for observing the dynamics of life building blocks like proteins, DNA and more.

Due to its operating mechanism, electron microscopy is known to be suitable for visualizing inert, dead samples, while living material needs to be chemically locked in place. IBS scientists broke this rule and visualized non-fixed chains of atoms, called polymers, swimming in a liquid inside graphene pockets. These consist of 3-5 graphene layers on the bottom and two on top. The sheets are impermeable to small molecules, and also prevent the electron beam from instantly harming the sample: the scientists had an average of 100 seconds to admire the dynamic movement of individual polymer molecules, before these were destroyed by the electron beam. During these valuable seconds, molecules change position, rearrange or "jump around".

Researchers in India and Japan have developed an improved method for using graphene-based transistors to detect disease-causing genes.

The team improved sensors that can detect genes through DNA hybridization, which occurs when a 'probe DNA' combines with its complementary 'target DNA.' Electrical conduction changes in the transistor when hybridization occurs. The improvement was done by attaching the probe DNA to the transistor through a drying process. 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.

A team of researchers at the University of California, San Diego, is developing a chip that has a graphene field effect transistor which contains a DNA probe. The double-stranded DNA has a sequence coding engineered to detect DNA or RNA with a specific single nucleotide mutation. An electrical signal is produced by the chip whenever this targeted type of DNA or RNA binds to the probe.

Attached to the probe is a regular strand of DNA, and bonded to this strand is a weak strand. The weak strand has four G’s in its sequence replaced with inosines, effectively weakening its bond. Together, the two strands create a double helix which operates DNA strand displacement. Any DNA strands which perfectly complement the normal strand will bind to the normal strand, and the weak strand will be knocked off. Because the DNA probe is connected to the graphene transistor, the chip is able to operate electronically. Eventually, this information could then be wirelessly transmitted to a mobile device.

Researchers at the National Institute of Standards and Technology (NIST) have simulated a new concept for rapid, accurate gene sequencing by pulling a DNA molecule through a tiny hole in graphene and detecting changes in electrical current. This new method might ultimately be faster and cheaper than conventional DNA sequencing.

The study suggests that the method could identify about 66 billion bases (the smallest units of genetic information) per second with 90% accuracy and no false positives. Conventional sequencing involves separating, copying, labeling and reassembling pieces of DNA to read the genetic information. The new NIST way offers a twist on the more recent "nanopore sequencing" idea of pulling DNA through a hole in specific materials, originally a protein. This concept is based on the passage of electrically charged particles (ions) through the pore and poses challenges such as unwanted electrical noise and inadequate selectivity.

Researchers from the University of Illinois at Urbana-Champaign (UIUC) have developed a new nanopore sequencing method based on graphene nanoribbons that detects double and single stranded DNA in different configurations. This graphene-based detector shows great sensitivity and holds promise for developing a portable, high-throughput sequencer that can also detect DNA morphological transformations.

In a nanopore sequencing reaction, DNA passes through a nanopore drilled in a membrane to which an electrical voltage is applied. When DNA goes through the pore, it causes dips in the electrical current. Reading the magnitude and duration of the electrical changes allows to identify the bases that go through.

Scientists at the University of Melbourne, the Australian Synchrotron and La Trobe University discovered that graphene can distinguish the four nucleobases that make up DNA and potentially be used to sequence DNA without the need for labels.

The researchers found that each nucleobase influenced the electronic structure of graphene in a measurably different way. When used together with a nanopore, a single DNA molecule would pass through the graphene-based electrical sensor enabling real-time, high-throughput sequencing of a single DNA molecule. The use of graphene to electrically sequence DNA promises to improve the speed, throughput, reliability and accuracy whilst reducing the price compared to current techniques.

Researchers from the Amrita Centre for Nanoscience and molecular Medicine in India developed a simple graphene-based method of thermally ablating highly resistant cancer cells. The method involves  biodegradable graphene nanoparticles, which were found to be able to convert non-ionizing radio waves into heat energy at microscopic levels.

This heat may be enough to eliminate proteins and DNA insode cancer cells, bypassing even the most resistant cancer-cell mechanisms. The method itself is minimally invasive and can be executed on any part of the body. Once the graphene platelets get to the target tumor cells, the radio waves sent from outside the body can supply a large amount of heat at highly localized levels and destroy all cellular proteins, which should lead to cell death.

Researchers at MIT and Harvard University found a way to use folded DNA to control the nanostructure of inorganic materials. DNA structures are built in a certain shape, then used as templates to create nanoscale patterns on sheets of graphene. This technique can further large-scale production of graphene electronic chips.

This technique forms DNA nanostructures with precisely planned shapes using short synthetic DNA strands called single-stranded tiles. Each of these tiles acts as an interlocking brick and binds with four designated neighbors. The researchers transferred the structural information encoded in DNA to graphene, using a relatively simple process that includes anchoring the DNA onto a graphene surface using a molecule called aminopyrine, which is similar in structure to graphene. The DNA is then coated with small clusters of silver along the surface, which allows a subsequent layer of gold to be deposited on top of the silver.

Researchers from Berkeley Lab and the University of California (UC) Berkeley have come up with a simple process for producing nanopores (about 2 nanometers in diameter) in a graphene membrane using the photothermal properties of gold nanorods.

The researchers aim to use this discovery to construct a direct DNA sequencing process, which will be simultaneously electrical and optical. This should facilitate a faster sequencing procedure, as traditional methods in which DNA components are sorted by an electrical current passing through nanopores on a silicon chip tend to get congested and slow, as information flowing through thousands of nanopores needs to be handled. Adding an optical component should, according to the researchers, help eliminate bottlenecks and speed up the sequencing process.

The National Institutes of Health (NIH) awarded a $880,000 grant for a University of Pennsylvania 2-year project that aims to develop fast and cost-effective genome sequencing. The project uses the DNA translocation process which threads DNA through nanopoers in a thin membrane - in this case a graphene nanoribbon (GNR) membrane.

A GNR is very useful for sequencing because it's thin and strong, and also its electrical properties enable to read the bases signals directly from the membrane as the DNA passes through the pore. We posted about this project last year, and it's great to see them receive more funding.