Tag Archives: DNA

DNA as a framework for rationally designed nanostructures

After publishing a June 15, 2016 post about taking DNA (deoxyribonucleic acid) beyond genetics, it seemed like a good to publish a companion piece featuring a more technical explanation of at least one way DNA might provide the base for living computers and robots. From a June 13, 2016 BrookHaven National Laboratory news release (also on EurekAlert),

A cube, an octahedron, a prism–these are among the polyhedral structures, or frames, made of DNA that scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have designed to connect nanoparticles into a variety of precisely structured three-dimensional (3D) lattices. The scientists also developed a method to integrate nanoparticles and DNA frames into interconnecting modules, expanding the diversity of possible structures.

These achievements, described in papers published in Nature Materials and Nature Chemistry, could enable the rational design of nanomaterials with enhanced or combined optical, electric, and magnetic properties to achieve desired functions.

“We are aiming to create self-assembled nanostructures from blueprints,” said physicist Oleg Gang, who led this research at the Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility at Brookhaven. “The structure of our nanoparticle assemblies is mostly controlled by the shape and binding properties of precisely designed DNA frames, not by the nanoparticles themselves. By enabling us to engineer different lattices and architectures without having to manipulate the particles, our method opens up great opportunities for designing nanomaterials with properties that can be enhanced by precisely organizing functional components. For example, we could create targeted light-absorbing materials that harness solar energy, or magnetic materials that increase information-storage capacity.”

The news release goes on to describe the frames,

Gang’s team has previously exploited DNA’s complementary base pairing–the highly specific binding of bases known by the letters A, T, G, and C that make up the rungs of the DNA double-helix “ladder”–to bring particles together in a precise way. Particles coated with single strands of DNA link to particles coated with complementary strands (A binds with T and G binds with C) while repelling particles coated with non-complementary strands.

They have also designed 3D DNA frames whose corners have single-stranded DNA tethers to which nanoparticles coated with complementary strands can bind. When the scientists mix these nanoparticles and frames, the components self-assemble into lattices that are mainly defined by the shape of the designed frame. The Nature Materials paper describes the most recent structures achieved using this strategy.

“In our approach, we use DNA frames to promote the directional interactions between nanoparticles such that the particles connect into specific configurations that achieve the desired 3D arrays,” said Ye Tian, lead author on the Nature Materials paper and a member of Gang’s research team. “The geometry of each particle-linking frame is directly related to the lattice type, though the exact nature of this relationship is still being explored.”

So far, the team has designed five polyhedral frame shapes–a cube, an octahedron, an elongated square bipyramid, a prism, and a triangular bypyramid–but a variety of other shapes could be created.

“The idea is to construct different 3D structures (buildings) from the same nanoparticle (brick),” said Gang. “Usually, the particles need to be modified to produce the desired structures. Our approach significantly reduces the structure’s dependence on the nature of the particle, which can be gold, silver, iron, or any other inorganic material.”

Nanoparticles (yellow balls) capped with short single-stranded DNA (blue squiggly lines) are mixed with polyhedral DNA frames (from top to bottom): cube, octahedron, elongated square bipyramid, prism, and triangular bipyramid. The frames' vertices are encoded with complementary DNA strands for nanoparticle binding. When the corresponding frames and particles mix, they form a framework. Courtesy of Brookhaven National Laboratory

Nanoparticles (yellow balls) capped with short single-stranded DNA (blue squiggly lines) are mixed with polyhedral DNA frames (from top to bottom): cube, octahedron, elongated square bipyramid, prism, and triangular bipyramid. The frames’ vertices are encoded with complementary DNA strands for nanoparticle binding. When the corresponding frames and particles mix, they form a framework. Courtesy of Brookhaven National Laboratory

There’s also a discussion about how DNA origami was used to design the frames,

To design the frames, the team used DNA origami, a self-assembly technique in which short synthetic strands of DNA (staple strands) are mixed with a longer single strand of biologically derived DNA (scaffold strand). When the scientists heat and cool this mixture, the staple strands selectively bind with or “staple” the scaffold strand, causing the scaffold strand to repeatedly fold over onto itself. Computer software helps them determine the specific sequences for folding the DNA into desired shapes.

The folding of the single-stranded DNA scaffold introduces anchoring points that contain free “sticky” ends–unpaired strings of DNA bases–where nanoparticles coated with complementary single-strand tethers can attach. These sticky ends can be positioned anywhere on the DNA frame, but Gang’s team chose the corners so that multiple frames could be connected.

For each frame shape, the number of DNA strands linking a frame corner to an individual nanoparticle is equivalent to the number of edges converging at that corner. The cube and prism frames have three strands at each corner, for example. By making these corner tethers with varying numbers of bases, the scientists can tune the flexibility and length of the particle-frame linkages.

The interparticle distances are determined by the lengths of the frame edges, which are tens of nanometers in the frames designed to date, but the scientists say it should be possible to tailor the frames to achieve any desired dimensions.

The scientists verified the frame structures and nanoparticle arrangements through cryo-electron microscopy (a type of microscopy conducted at very low temperatures) at the CFN and Brookhaven’s Biology Department, and x-ray scattering at the National Synchrotron Light Source II (NSLS-II), a DOE Office of Science User Facility at Brookhaven.

The team started with a relatively simple form (from the news release),

In the Nature Chemistry paper, Gang’s team described how they used a similar DNA-based approach to create programmable two-dimensional (2D), square-like DNA frames around single nanoparticles.

DNA strands inside the frames provide coupling to complementary DNA on the nanoparticles, essentially holding the particle inside the frame. Each exterior side of the frame can be individually encoded with different DNA sequences. These outer DNA strands guide frame-frame recognition and connection.

Gang likens these DNA-framed nanoparticle modules to Legos whose interactions are programmed: “Each module can hold a different kind of nanoparticle and interlock to other modules in different but specific ways, fully determined by the complementary pairing of the DNA bases on the sides of the frame.”

In other words, the frames not only determine if the nanoparticles will connect but also how they will connect. Programming the frame sides with specific DNA sequences means only frames with complementary sequences can link up.

Mixing different types of modules together can yield a variety of structures, similar to the constructs that can be generated from Lego pieces. By creating a library of the modules, the scientists hope to be able to assemble structures on demand.

Finally, the discussion turns to the assembly of multifuctional nanomaterials (from the news release),

The selectivity of the connections enables different types and sizes of nanoparticles to be combined into single structures.

The geometry of the connections, or how the particles are oriented in space, is very important to designing structures with desired functions. For example, optically active nanoparticles can be arranged in a particular geometry to rotate, filter, absorb, and emit light–capabilities that are relevant for energy-harvesting applications, such as display screens and solar panels.

By using different modules from the “library,” Gang’s team demonstrated the self-assembly of one-dimensional linear arrays, “zigzag” chains, square-shaped and cross-shaped clusters, and 2D square lattices. The scientists even generated a simplistic nanoscale model of Leonardo da Vinci’s Vitruvian Man.

“We wanted to demonstrate that complex nanoparticle architectures can be self-assembled using our approach,” said Gang.

Again, the scientists used sophisticated imaging techniques–electron and atomic force microscopy at the CFN and x-ray scattering at NSLS-II–to verify that their structures were consistent with the prescribed designs and to study the assembly process in detail.

“Although many additional studies are required, our results show that we are making advances toward our goal of creating designed matter via self-assembly, including periodic particle arrays and complex nanoarchitectures with freeform shapes,” said Gang. “Our approach is exciting because it is a new platform for nanoscale manufacturing, one that can lead to a variety of rationally designed functional materials.”

Here’s an image illustrating among other things da Vinci’s Vitruvian Man,

A schematic diagram (left) showing how a nanoparticle (yellow ball) is incorporated within a square-like DNA frame. The DNA strands inside the frame (blue squiggly lines) are complementary to the DNA strands on the nanoparticle; the colored strands on the outer edges of the frame have different DNA sequences that determine how the DNA-framed nanoparticle modules can connect. The architecture shown (middle) is a simplistic nanoscale representation of Leonardo da Vinci's Vitruvian Man, assembled from several module types. The scientists used atomic force microscopy to generate the high-magnification image of this assembly (right). Courtesy Brookhaven National Laboratory

A schematic diagram (left) showing how a nanoparticle (yellow ball) is incorporated within a square-like DNA frame. The DNA strands inside the frame (blue squiggly lines) are complementary to the DNA strands on the nanoparticle; the colored strands on the outer edges of the frame have different DNA sequences that determine how the DNA-framed nanoparticle modules can connect. The architecture shown (middle) is a simplistic nanoscale representation of Leonardo da Vinci’s Vitruvian Man, assembled from several module types. The scientists used atomic force microscopy to generate the high-magnification image of this assembly (right). Courtesy Brookhaven National Laboratory

I enjoy the overviews provided by various writers and thinkers in the field but it’s details such as these that are often most compelling to me.

Taking DNA beyond genetics with living computers and nanobots

You might want to keep a salt shaker with you while reading a June 7, 2016 essay by Matteo Palma (Queen Mary’s University of London) about nanotechnology and DNA on The Conversation website (h/t June 7, 2016 news item on Nanowerk).

This is not a ‘hype’ piece as Palma backs every claim with links to the research while providing a good overview of some very exciting work but the mood is a bit euphoric so you may want to keep the earlier mentioned salt shaker nearby.

Palma offers a very nice beginner introduction especially helpful for someone who only half-remembers their high school biology (from the June 7, 2016 essay)

DNA is one of the most amazing molecules in nature, providing a way to carry the instructions needed to create almost any lifeform on Earth in a microscopic package. Now scientists are finding ways to push DNA even further, using it not just to store information but to create physical components in a range of biological machines.

Deoxyribonucleic acid or “DNA” carries the genetic information that we, and all living organisms, use to function. It typically comes in the form of the famous double-helix shape, made up of two single-stranded DNA molecules folded into a spiral. Each of these is made up of a series of four different types of molecular component: adenine (A), guanine (G), thymine (T), and cytosine (C).

Genes are made up from different sequences of these building block components, and the order in which they appear in a strand of DNA is what encodes genetic information. But by precisely designing different A,G,T and C sequences, scientists have recently been able to develop new ways of folding DNA into different origami shapes, beyond the conventional double helix.

This approach has opened up new possibilities of using DNA beyond its genetic and biological purpose, turning it into a Lego-like material for building objects that are just a few billionths of a metre in diameter (nanoscale). DNA-based materials are now being used for a variety of applications, ranging from templates for electronic nano-devices, to ways of precisely carrying drugs to diseased cells.

He highlights some Canadian work,

Designing electronic devices that are just nanometres in size opens up all sorts of possible applications but makes it harder to spot defects. As a way of dealing with this, researchers at the University of Montreal have used DNA to create ultrasensitive nanoscale thermometers that could help find minuscule hotspots in nanodevices (which would indicate a defect). They could also be used to monitor the temperature inside living cells.

The nanothermometers are made using loops of DNA that act as switches, folding or unfolding in response to temperature changes. This movement can be detected by attaching optical probes to the DNA. The researchers now want to build these nanothermometers into larger DNA devices that can work inside the human body.

He also mentions the nanobots that will heal your body (according to many works of fiction),

Researchers at Harvard Medical School have used DNA to design and build a nanosized robot that acts as a drug delivery vehicle to target specific cells. The nanorobot comes in the form of an open barrel made of DNA, whose two halves are connected by a hinge held shut by special DNA handles. These handles can recognise combinations of specific proteins present on the surface of cells, including ones associated with diseases.

When the robot comes into contact with the right cells, it opens the container and delivers its cargo. When applied to a mixture of healthy and cancerous human blood cells, these robots showed the ability to target and kill half of the cancer cells, while the healthy cells were left unharmed.

Palma is describing a very exciting development and there are many teams worldwide working on ways to make drugs more effective and less side effect-ridden. However there does seem to be a bit of a problem with targeted drug delivery as noted in my April 27, 2016 posting,

According to an April 27, 2016 news item on Nanowerk researchers at the University of Toronto (Canada) along with their collaborators in the US (Harvard Medical School) and Japan (University of Tokyo) have determined that less than 1% of nanoparticle-based drugs reach their intended destination …

Less than 1%? Admittedly, nanoparticles are not the same as nanobots but the problem is in the delivery, from my April 27, 2016 posting,

… the authors argue that, in order to increase nanoparticle delivery efficiency, a systematic and coordinated long-term strategy is necessary. To build a strong foundation for the field of cancer nanomedicine, researchers will need to understand a lot more about the interactions between nanoparticles and the body’s various organs than they do today. …

I imagine nanobots will suffer a similar fate since the actual delivery mechanism to a targeted cell is still a mystery.

I quite enjoyed Palma’s essay and appreciated the links he provided. My only proviso, keep a salt shaker nearby. That rosy future is going take a while to get here.

The Leonardo Project and the master’s DNA (deoxyribonucleic acid)

I’ve never really understood the mania for digging up bodies of famous people in history and trying to ascertain how the person really died or what kind of diseases they may have had but the practice fascinates me. The latest famous person to be subjected to a forensic inquiry centuries after death is Leonardo da Vinci. A May 5, 2016 Human Evolution (journal) news release on EurekAlert provides details,

A team of eminent specialists from a variety of academic disciplines has coalesced around a goal of creating new insight into the life and genius of Leonardo da Vinci by means of authoritative new research and modern detective technologies, including DNA science.

The Leonardo Project is in pursuit of several possible physical connections to Leonardo, beaming radar, for example, at an ancient Italian church floor to help corroborate extensive research to pinpoint the likely location of the tomb of his father and other relatives. A collaborating scholar also recently announced the successful tracing of several likely DNA relatives of Leonardo living today in Italy (see endnotes).

If granted the necessary approvals, the Project will compare DNA from Leonardo’s relatives past and present with physical remnants — hair, bones, fingerprints and skin cells — associated with the Renaissance figure whose life marked the rebirth of Western civilization.

The Project’s objectives, motives, methods, and work to date are detailed in a special issue of the journal Human Evolution, published coincident with a meeting of the group hosted in Florence this week under the patronage of Eugenio Giani, President of the Tuscan Regional Council (Consiglio Regionale della Toscana).

The news release goes on to provide some context for the work,

Born in Vinci, Italy, Leonardo died in 1519, age 67, and was buried in Amboise, southwest of Paris. His creative imagination foresaw and described innovations hundreds of years before their invention, such as the helicopter and armored tank. His artistic legacy includes the iconic Mona Lisa and The Last Supper.

The idea behind the Project, founded in 2014, has inspired and united anthropologists, art historians, genealogists, microbiologists, and other experts from leading universities and institutes in France, Italy, Spain, Canada and the USA, including specialists from the J. Craig Venter Institute of California, which pioneered the sequencing of the human genome.

The work underway resembles in complexity recent projects such as the successful search for the tomb of historic author Miguel de Cervantes and, in March 2015, the identification of England’s King Richard III from remains exhumed from beneath a UK parking lot, fittingly re-interred 500 years after his death.

Like Richard, Leonardo was born in 1452, and was buried in a setting that underwent changes in subsequent years such that the exact location of the grave was lost.

If DNA and other analyses yield a definitive identification, conventional and computerized techniques might reconstruct the face of Leonardo from models of the skull.”

In addition to Leonardo’s physical appearance, information potentially revealed from the work includes his ancestry and additional insight into his diet, state of health, personal habits, and places of residence.

According to the news release, the researchers have an agenda that goes beyond facial reconstruction and clues about  ancestry and diet,

Beyond those questions, and the verification of Leonardo’s “presumed remains” in the chapel of Saint-Hubert at the Château d’Amboise, the Project aims to develop a genetic profile extensive enough to understand better his abilities and visual acuity, which could provide insights into other individuals with remarkable qualities.

It may also make a lasting contribution to the art world, within which forgery is a multi-billion dollar industry, by advancing a technique for extracting and sequencing DNA from other centuries-old works of art, and associated methods of attribution.

Says Jesse Ausubel, Vice Chairman of the Richard Lounsbery Foundation, sponsor of the Project’s meetings in 2015 and 2016: “I think everyone in the group believes that Leonardo, who devoted himself to advancing art and science, who delighted in puzzles, and whose diverse talents and insights continue to enrich society five centuries after his passing, would welcome the initiative of this team — indeed would likely wish to lead it were he alive today.”

The researchers aim to have the work complete by 2019,

In the journal, group members underline the highly conservative, precautionary approach required at every phase of the Project, which they aim to conclude in 2019 to mark the 500th anniversary of Leonardo’s death.

For example, one objective is to verify whether fingerprints on Leonardo’s paintings, drawings, and notebooks can yield DNA consistent with that extracted from identified remains.

Early last year, Project collaborators from the International Institute for Humankind Studies in Florence opened discussions with the laboratory in that city where Leonardo’s Adoration of the Magi has been undergoing restoration for nearly two years, to explore the possibility of analyzing dust from the painting for possible DNA traces. A crucial question is whether traces of DNA remain or whether restoration measures and the passage of time have obliterated all evidence of Leonardo’s touch.

In preparation for such analysis, a team from the J. Craig Venter Institute and the University of Florence is examining privately owned paintings believed to be of comparable age to develop and calibrate techniques for DNA extraction and analysis. At this year’s meeting in Florence, the researchers also described a pioneering effort to analyze the microbiome of a painting thought to be about five centuries old.

If human DNA can one day be obtained from Leonardo’s work and sequenced, the genetic material could then be compared with genetic information from skeletal or other remains that may be exhumed in the future.

Here’s a list of the participating organizations (from the news release),

  • The Institut de Paléontologie Humaine, Paris
  • The International Institute for Humankind Studies, Florence
  • The Laboratory of Molecular Anthropology and Paleogenetics, Biology Department, University of Florence
  • Museo Ideale Leonardo da Vinci, in Vinci, Italy
  • J. Craig Venter Institute, La Jolla, California
  • Laboratory of Genetic Identification, University of Granada, Spain
  • The Rockefeller University, New York City

You can find the special issue of Human Evolution (HE Vol. 31, 2016 no. 3) here. The introductory essay is open access but the other articles are behind a paywall.

Disinfectant for backyard pools could be key to new nanomaterials

Research from McGill University (Québec, Canada) focuses on cyanuric acid, one of the chemicals used to disinfect backyard pools. according to a March 1, 2016 McGill University news release (received by email; it can also be found in a March 1, 2016 news item on Nanowerk *and on EurekAlert*),

Cyanuric acid is commonly used to stabilize chlorine in backyard pools; it binds to free chlorine and releases it slowly in the water. But researchers at McGill University have now discovered that this same small, inexpensive molecule can also be used to coax DNA into forming a brand new structure: instead of forming the familiar double helix, DNA’s nucleobases — which normally form rungs in the DNA ladder — associate with cyanuric acid molecules to form a triple helix.

The discovery “demonstrates a fundamentally new way to make DNA assemblies,” says Hanadi Sleiman, Canada Research Chair in DNA Nanoscience at McGill and senior author of the study, published in Nature Chemistry. “This concept may apply to many other molecules, and the resulting DNA assemblies could have applications in a range of technologies.”

The DNA alphabet, composed of the four letters A, T, G and C, is the underlying code that gives rise to the double helix famously discovered by Watson and Crick more than 60 years ago. The letters, or bases, of DNA can also interact in other ways to form a variety of DNA structures used by scientists in nanotechnology applications – quite apart from DNA’s biological role in living cells.

For years, scientists have sought to develop a larger, designer alphabet of DNA bases that would enable the creation of more DNA structures with unique, new properties. For the most part, however, devising these new molecules has involved costly and complex procedures.

The road to the McGill team’s discovery began some eight years ago, when Sleiman mentioned to others in her lab that cyanuric acid might be worth experimenting with because of its properties. The molecule has three faces with the same binding features as thymine (T in the DNA alphabet), the natural complement to adenine (A).  “One of my grad students tried it,” she recalls, “and came back and said he saw fibres” through an atomic force microscope.

The researchers later discovered that these fibres have a unique underlying structure. Cyanuric acid is able to coax strands composed of adenine bases into forming a novel motif in DNA assembly. The adenine and cyanuric acid units associate into flower-like rosettes; these form the cross-section of a triple helix.  The strands then combine to form long fibres.

“The nanofibre material formed in this way is easy to access, abundant and highly structured,” says Nicole Avakyan, a PhD student in Sleiman’s lab and first author of the study. “With further development, we can envisage a variety of applications of this material, from medicinal chemistry to tissue engineering and materials science.”

Here’s a link to and a citation for the paper,

Reprogramming the assembly of unmodified DNA with a small molecule by Nicole Avakyan, Andrea A. Greschner, Faisal Aldaye, Christopher J. Serpell, Violeta Toader,    Anne Petitjean, & Hanadi F. Sleiman. Nature Chemistry (2016) doi:10.1038/nchem.2451 Published online 22 February 2016

This paper is behind a paywall.

*’also on EurekAlert’ added on March 2, 2016.

Shape-shifting nanoparticles for better chemotherapy from the University of Toronto (Canada)

A research team from the University of Toronto and its shape-shifting nanoparticles are being touted in a Feb. 19, 2016 news item on Nanowerk,

Chemotherapy isn’t supposed to make your hair fall out — it’s supposed to kill cancer cells. A new molecular delivery system created at U of T [University of Toronto] Engineering could help ensure that chemotherapy drugs get to their target while minimizing collateral damage.

Many cancer drugs target fast-growing cells. Injected into a patient, they swirl around in the bloodstream acting on fast-growing cells wherever they find them. That includes tumours, but unfortunately also hair follicles, the lining of your digestive system, and your skin.

U of T Engineering Professor Warren Chan has spent the last decade figuring out how to deliver chemotherapy drugs into tumours — and nowhere else. Now his lab has designed a set of nanoparticles attached to strands of DNA that can change shape to gain access to diseased tissue.

A Feb. 18, 2016 University of Toronto news release (also on EurekAlert), which originated the news item, expands on the theme,

“Your body is basically a series of compartments,” says Chan. “Think of it as a giant house with rooms inside. We’re trying to figure out how to get something that’s outside, into one specific room. One has to develop a map and a system that can move through the house where each path to the final room may have different restrictions such as height and width.”

One thing we know about cancer: no two tumours are identical. Early-stage breast cancer, for example, may react differently to a given treatment than pancreatic cancer, or even breast cancer at a more advanced stage. Which particles can get inside which tumours depends on multiple factors such as the particle’s size, shape and surface chemistry.

Chan and his research group have studied how these factors dictate the delivery of small molecules and nanotechnologies to tumours, and have now designed a targeted molecular delivery system that uses modular nanoparticles whose shape, size and chemistry can be altered by the presence of specific DNA sequences.

“We’re making shape-changing nanoparticles,” says Chan. “They’re a series of building blocks, kind of like a LEGO set.” The component pieces can be built into many shapes, with binding sites exposed or hidden. They are designed to respond to biological molecules by changing shape, like a key fitting into a lock.

These shape-shifters are made of minuscule chunks of metal with strands of DNA attached to them. Chan envisions that the nanoparticles will float around harmlessly in the blood stream, until a DNA strand binds to a sequence of DNA known to be a marker for cancer. When this happens, the particle changes shape, then carries out its function: it can target the cancer cells, expose a drug molecule to the cancerous cell, tag the cancerous cells with a signal molecule, or whatever task Chan’s team has designed the nanoparticle to carry out.

“We were inspired by the ability of proteins to alter their conformation — they somehow figure out how to alleviate all these delivery issues inside the body,” says Chan. “Using this idea, we thought, ‘Can we engineer a nanoparticle to function like a protein, but one that can be programmed outside the body with medical capabilities?’”

Applying nanotechnology and materials science to medicine, and particularly to targeted drug delivery, is still a relatively new concept, but one Chan sees as full of promise. The real problem is how to deliver enough of the nanoparticles directly to the cancer to produce an effective treatment.

“Here’s how we look at these problems: it’s like you’re going to Vancouver from Toronto, but no one tells you how to get there, no one gives you a map, or a plane ticket, or a car — that’s where we are in this field,” he says. “The idea of targeting drugs to tumours is like figuring out how to go to Vancouver. It’s a simple concept, but to get there isn’t simple if not enough information is provided.”

“We’ve only scratched the surface of how nanotechnology ‘delivery’ works in the body, so now we’re continuing to explore different details of why and how tumours and other organs allow or block certain things from getting in,” adds Chan.

He and his group plan to apply the delivery system they’ve designed toward personalized nanomedicine — further tailoring their particles to deliver drugs to your precise type of tumour, and nowhere else.

Here are links to and citations for the team’s two published papers,

DNA-controlled dynamic colloidal nanoparticle systems for mediating cellular interaction by Seiichi Ohta, Dylan Glancy, Warren C. W. Chan. Science  19 Feb 2016: Vol. 351, Issue 6275, pp. 841-845 DOI: 10.1126/science.aad4925

Tailoring nanoparticle designs to target cancer based on tumor pathophysiology by Edward A. Sykes, Qin Dai, Christopher D. Sarsons, Juan Chen, Jonathan V. Rocheleau, David M. Hwang, Gang Zheng, David T. Cramb, Kristina D. Rinker, and Warren C. W. Chan. PNAS     doi: 10.1073/pnas.1521265113 published online Feb. 16, 2016.

Both papers are behind paywalls.

A nanoparticle ‘printing press’

This research comes from Montréal, Canada via a Jan. 7, 2016 McGill University news release (also on EurekAlert*),

Gold nanoparticles have unusual optical, electronic and chemical properties, which scientists are seeking to put to use in a range of new technologies, from nanoelectronics to cancer treatments.

Some of the most interesting properties of nanoparticles emerge when they are brought close together – either in clusters of just a few particles or in crystals made up of millions of them. Yet particles that are just millionths of an inch in size are too small to be manipulated by conventional lab tools, so a major challenge has been finding ways to assemble these bits of gold while controlling the three-dimensional shape of their arrangement.

One approach that researchers have developed has been to use tiny structures made from synthetic strands of DNA to help organize nanoparticles. Since DNA strands are programmed to pair with other strands in certain patterns, scientists have attached individual strands of DNA to gold particle surfaces to create a variety of assemblies. But these hybrid gold-DNA nanostructures are intricate and expensive to generate, limiting their potential for use in practical materials. The process is similar, in a sense, to producing books by hand.

Enter the nanoparticle equivalent of the printing press. It’s efficient, re-usable and carries more information than previously possible. In results reported online in Nature Chemistry, researchers from McGill’s Department of Chemistry outline a procedure for making a DNA [deoxyribonucleic acid] structure with a specific pattern of strands coming out of it; at the end of each strand is a chemical “sticky patch.”  When a gold nanoparticle is brought into contact to the DNA nanostructure, it sticks to the patches. The scientists then dissolve the assembly in distilled water, separating the DNA nanostructure into its component strands and leaving behind the DNA imprint on the gold nanoparticle. …

The researchers have made an illustration of their concept available,

Credit: Thomas Edwardson

Credit: Thomas Edwardson

“These encoded gold nanoparticles are unprecedented in their information content,” says senior author Hanadi Sleiman, who holds the Canada Research Chair in DNA Nanoscience. “The DNA nanostructures, for their part, can be re-used, much like stamps in an old printing press.”

The news release includes suggestions for possible future applications,

From stained glass to optoelectronics

Some of the properties of gold nanoparticles have been recognized for centuries.  Medieval artisans added gold chloride to molten glass to create the ruby-red colour in stained-glass windows – the result, as chemists figured out much later, of the light-scattering properties of tiny gold particles.

Now, the McGill researchers hope their new production technique will help pave the way for use of DNA-encoded nanoparticles in a range of cutting-edge technologies. First author Thomas Edwardson says the next step for the lab will be to investigate the properties of structures made from these new building blocks. “In much the same way that atoms combine to form complex molecules, patterned DNA gold particles can connect to neighbouring particles to form well-defined nanoparticle assemblies.”

These could be put to use in areas including optoelectronic nanodevices and biomedical sciences, the researchers say. The patterns of DNA strands could, for example, be engineered to target specific proteins on cancer cells, and thus serve to detect cancer or to selectively destroy cancer cells.

Here’s a link to and a citation for the paper,

Transfer of molecular recognition information from DNA nanostructures to gold nanoparticles by Thomas G. W. Edwardson, Kai Lin Lau, Danny Bousmail, Christopher J. Serpell, & Hanadi F. Sleiman. Nature Chemistry (2016)  doi:10.1038/nchem.2420 Published online 04 January 2016

This paper is behind a paywall.

*’also on EurekAlert’ added on Jan. 8, 2016.

Enzymatic fuel cells with ultrasmall gold nanocluster

Scientists at the US Department of Energy’s Los Alamos National Laboratory have developed a DNA-templated gold nanocluster (AuNC) for more efficient biofuel cell design (Note: A link has been removed). From a Sept. 24, 2015 news item on ScienceDaily,

With fossil-fuel sources dwindling, better biofuel cell design is a strong candidate in the energy field. In research published in the Journal of the American Chemical Society (“A Hybrid DNA-Templated Gold Nanocluster For Enhanced Enzymatic Reduction of Oxygen”), Los Alamos researchers and external collaborators synthesized and characterized a new DNA-templated gold nanocluster (AuNC) that could resolve a critical methodological barrier for efficient biofuel cell design.

Here’s an image illustrating the DNA-templated gold nanoclusters,

Caption: Gold nanoclusters (~1 nm) are efficient mediators of electron transfer between co-self-assembled enzymes and carbon nanotubes in an enzyme fuel cell. The efficient electron transfer from this quantized nano material minimizes the energy waste and improves the kinetics of the oxygen reduction reaction, toward a more efficient fuel cell cycle. Credit: Los Alamos National Laboratory

Caption: Gold nanoclusters (~1 nm) are efficient mediators of electron transfer between co-self-assembled enzymes and carbon nanotubes in an enzyme fuel cell. The efficient electron transfer from this quantized nano material minimizes the energy waste and improves the kinetics of the oxygen reduction reaction, toward a more efficient fuel cell cycle.
Credit: Los Alamos National Laboratory

A Sept. 24, 2015 Los Alamos National Laboratory news release, which originated the news item, provides more details,

“Enzymatic fuel cells and nanomaterials show great promise and as they can operate under environmentally benign neutral pH conditions, they are a greener alternative to existing alkaline or acidic fuel cells, making them the subject of worldwide research endeavors,” said Saumen Chakraborty, a scientist on the project. “Our work seeks to boost electron transfer efficiency, creating a potential candidate for the development of cathodes in enzymatic fuel cells.”

Ligands, molecules that bind to a central metal atom, are necessary to form stable nanoclusters. For this study, the researchers chose single-stranded DNA as the ligand, as DNA is a natural nanoscale material having high affinity for metal cations and can be used to assembly the cluster to other nanoscale material such as carbon nanotubes.

In enzymatic fuel cells, fuel is oxidized on the anode, while oxygen reduction reactions take place on the cathode, often using multi copper oxidases. Enzymatic fuel cell performance depends critically on how effectively the enzyme active sites can accept and donate electrons from the electrode by direct electron transfer (ET). However, the lack of effective ET between the enzyme active sites, which are usually buried ~10Å from their surface, and the electrode is a major barrier to their development. Therefore, effective mediators of this electron transfer are needed.

The team developed a new DNA-templated gold nanocluster (AuNC) that enhanced electron transfer. This novel role of the AuNC as enhancer of electron transfer at the enzyme-electrode interface could be effective for cathodes in enzymatic fuel cells, thus removing a critical methodological barrier for efficient biofuel cell design.

Possessing many unique properties due to their discrete electron state distributions, metal nanoclusters (<1.5 nm diameter; ~2-144 atoms of gold, silver, platinum, or copper) show application in many fields.

Hypothesizing that due to the ultra-small size (the clusters are ~7 atoms, ~0.9 nm in diameter), and unique electrochemical properties, the AuNC can facilitate electron transfer to an oxygen-reduction reaction enzyme-active site and therefore, lower the overpotential of the oxygen reaction. Overpotential is the extra amount of energy required to drive an electrochemical reaction.

Ideally, it is desirable that all electrochemical reactions have minimal to no overpotential, but in reality they all have some. Therefore, to design an efficient electrocatalyst (for reduction or oxidation) we want to design it so that the reaction can proceed with a minimal amount of extra, applied energy.

When self assembled with bilirubin oxidase and carbon nanotubes, the AuNC acts to enhance the electron transfer, and it lowers the overpotential of oxygen reduction by a significant ~15 mV (as opposed to ~1-2 mV observed using other types of mediators) compared to the enzyme alone. The AuNC also causes significant enhancement of electrocatalytic current densities. Proteins are electronically insulating (they are complex, greasy and large), so the use of carbon nanotubes helps the enzyme stick to the electrode as well as to facilitate electron transfer.

Although gold nanoclusters have been used in chemical catalysis, this is the first time that we demonstrate they can also act as electron relaying agents to enzymatic oxygen reduction reaction monitored by electrochemistry.

Finally, the presence of AuNC does not perturb the mechanism of enzymatic O2 reduction. Such unique application of AuNC as facilitator of ET by improving thermodynamics and kinetics of O2 reduction is unprecedented.

Here’s a link to and a citation for the paper,

A Hybrid DNA-Templated Gold Nanocluster For Enhanced Enzymatic Reduction of Oxygen by Saumen Chakraborty, Sofia Babanova, Reginaldo C. Rocha, Anil Desireddy, Kateryna Artyushkova, Amy E. Boncella, Plamen Atanassov, and Jennifer S. Martinez. J. Am. Chem. Soc., 2015, 137 (36), pp 11678–11687 DOI: 10.1021/jacs.5b05338 Publication Date (Web): August 19, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

What’s in your DNA (deoxyribonucleic acid)? an art auction at Christies

For this item, I have David Bruggeman’s Sept. 24, 2015 posting on his Pasco Phronesis blog to thank,

As part of a fundraising project for a building at the Francis Crick Institute, Christie’s will hold an auction for 30 double-helix sculptures on September 30 (H/T ScienceInsider).

David has embedded a video featuring some of the artists and their works in his posting. By contrast, here are a few pictures of the DNA (deoxyribonucleic acid) art objects from the Cancer Research UK’s DNA Trail page,

For our London Art trail, which ran from 29 June – 6 September 2015, we asked internationally renowned artists to design a beautiful double helix sculpture inspired by the question: What’s in your DNA? Take a look at their sculptures and find out more about the artists’ inspirations.

This one is called The Journey and is by Gary Portell,

DNA_The Journey

His inspiration is: “My design is based on two symbols, the swallow who shares my journey from Africa to England and the hand print. The hand print as a symbol of creation and the swallow reflects the traveller.

This one by Thiery Noir is titled Double Helix Noir.

DNA_DoubleHelixNoir

The inspiration is: For this sculpture, Noir wanted to pay tribute to the memory of his former assistant, Lisa Brown, who was affected by breast cancer and who passed away in July 2001, at the young age of 31 years old.

Growing Stem is by Orla Kiely,

CNA_GrowingStem

The inspiration is: I find inspiration in many things, but especially love nature with the abundance of colourful flowers, leaves, and stems. Applying our multi stem onto the DNA spiral seemed a natural choice as it represents positivity and growth: qualities that are so relevant for cancer research.

Double Dutch Delftblue DNA is by twins, Chris and Xand van Tulleken.

DNA_DoubleDutchDelftblue

The inspiration is: The recurrent motifs of Delft tiles reference those of DNA. Our inspiration was the combination of our family’s DNA, drawing on Dutch and Canadian origins, and the fact that twins have shared genomes.  (With thanks to Anthony van Tulleken)

Ted Baker’s Ted’s Helix of Haberdashery,

DNA_TedsHelixOfHaberdashery

Inspiration is: Always a fan of spinning a yarn, Ted Baker’s Helix of Haberdashery sculpture unravels the tale of his evolution from shirt specialist to global lifestyle brand. Ted’s DNA is represented as a cascading double helix of pearlescent buttons, finished with a typically playful story-telling flourish.

Finally, What Mad Pursuit is by Kindra Crick,

DNA_WhatMadPursuit

Inspiration is: What Mad Pursuit explores the creative possibilities achievable through the intermingling of art, science and imagination in the quest for knowledge. The piece is inspired by my family’s contribution to the discovery of the structure of DNA.

Aparna Vidyasagar interviewed Kindra Crick in a Sept. 24, 2015 Q&A for ScienceInsider (Note: Links have been removed),

Kindra Crick, granddaughter of Francis Crick, the co-discoverer of DNA’s structure, is one of more than 20 artists contributing sculptures to an auction fundraiser for a building at the new Francis Crick Institute. The auction is being organized by Cancer Research UK and will be held at Christie’s in London on 30 September. The auction will continue online until 13 October.

The new biomedical research institute, named for the Nobel laureate who died in 2004, aims to develop prevention strategies and treatments for diseases including cancer. It is a consortium of six partners, including Cancer Research UK.

Earlier this year, Cancer Research UK asked about two dozen artists—including Chinese superstar Ai Weiwei—to answer the question “What’s in your DNA?” through a sculpture based on DNA’s double helix structure. …

Q: “What’s in your DNA?” How did you build your sculpture around that question?

A: When I was given the theme, I thought this was a wonderful project for me, considering my family history. Also, in my own art practice I try to express the wonder and the process of scientific inquiry. This draws on my backgrounds; in molecular biology from when I was at Princeton [University], and in art while going to the School of the Art Institute of Chicago.

I was influenced by my grandparents, Francis Crick and Odile Crick. He was the scientist and she was the artist. My grandfather worked on elucidating the structure of DNA, and my grandmother, Odile, was the one to draw the first image of DNA. The illustration was used for the 1953 paper that my grandfather wrote with James Watson. So, there’s a rich history there that I can draw from, in terms of what’s in my DNA.

Should you be interested in bidding on one of the pieces, you can go to Christie’s What’s in your DNA webpage,

ONLINE AUCTION IS LIVE: 30 September – 13 October 2015

Good luck!

David Bruggeman has put in a request (from his Sept. 24, 2015 posting),

… if you become aware of human trials for 3D bioprinting, please give a holler.  I may now qualify.

Good luck David!

Science cakery

I have to thank Dean Burnett for his science cake extravagance on the Guardian science blogs. Here’s a few pictures of cake to tantalize you from Burnett’s Aug. 12, 2015 posting,

An evolution-of-life cake from @OxUniEarthSci Palaeontology Group. Bizarre how this life-sciences cake seems to defy physics with its structure. Photograph: @JackJMatthews

An evolution-of-life cake from @OxUniEarthSci Palaeontology Group. Bizarre how this life-sciences cake seems to defy physics with its structure.
Photograph: @JackJMatthews

A cake shaped like a subject entering an MRI scanner for @ImanovaImaging’s 1st birthday party. Because why not? Photograph: @M_Wall

A cake shaped like a subject entering an MRI scanner for @ImanovaImaging’s 1st birthday party. Because why not?
Photograph: @M_Wall

Katie Watkins created TMS coils on talking brains. For the record, it is not necessary or even helpful for the brain to be exposed during TMS. Photograph: Kate Watkins

Katie Watkins created TMS coils on talking brains. For the record, it is not necessary or even helpful for the brain to be exposed during TMS. Photograph: Kate Watkins

Katie Grifiths, posing with a DNA cake made by her sister Emma. What’s with these biology-themed cakes and their ability to overrule gravity? Do NASA know about this? Photograph: Katie Griffiths

Katie Grifiths, posing with a DNA cake made by her sister Emma. What’s with these biology-themed cakes and their ability to overrule gravity? Do NASA know about this?
Photograph: Katie Griffiths

Marilyn Audlsey produced this particles-in-a-cloud-chamber ginger cake. I’m not even going to pretend to know what that is, but it makes for a nice looking cake. Photograph: Marilyn Audsley

Marilyn Audlsey produced this particles-in-a-cloud-chamber ginger cake. I’m not even going to pretend to know what that is, but it makes for a nice looking cake. Photograph: Marilyn Audsley

And this is the last one I’m including,

Sara Barnes did this @ATLASexperiment. At last, the money spent on the Lare Hadron Collider starts to show useful results. Photograph: Sarah Barnes

Sara Barnes did this @ATLASexperiment. At last, the money spent on the Lare Hadron Collider starts to show useful results.
Photograph: Sarah Barnes

Burnett has many more areas of science memorialized in cake in his Aug. 12, 2015 posting.

I last featured science and cakes in a March 31, 2012 posting about the periodic table of elements and cupcakes. On a closely related note, I wrote about mathematics and baking in a June 28, 2013 posting.