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October 18th, 2011

The fuzzy line between biology and materials science: Using DNA to build new materials

Published on October 18th, 2011 | By: Eileen De Guire

NYU scientists have developed artificial structures consisting of triple helix molecules containing three DNA double helices that can self-replicate. In the above illustration, two BTX domains are paired by two lateral connections (another two existing connections are not shown). The cross-section view shows two of the four helices that are formed by the lateral cohesive interactions.. Credit: Paul Chaikin, Nadrian Seeman; Nature.

I assume the Materials Genome Initiative moniker was chosen to reference the Human Genome Project, which had the goal of mapping the human genome into its 6 billion or so nucleotides. The MGI proposes to go the other way—to start with elements, the basic building blocks of matter—and combine them to build engineered materials.

In a rather interesting twist, a group at New York University has bridged the metaphorical gap by showing that DNA can be used to assemble complex new materials that are not necessarily organic.

This is some pretty fancy science, and the press release explains it best (edited, somewhat, for clarity).

To demonstrate this self-replication process, the NYU scientists created artificial DNA “tile motifs” —short, nanometer-scale arrangements of DNA. Each tile serves as a letter— say an “A” or a “B”—that recognizes and binds to complementary letters A’ or B’.

In the natural world, the DNA replication process involves complementary matches between bases-adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C)—to form its familiar double helix. By contrast, the NYU researchers’ tile motif, called BTX (bent triple helix molecules, containing three DNA double helices), are unlike DNA because the BTX code is not limited to four letters: In principle, it can contain quadrillions of different letters and tiles that pair … to form a six-helix bundle.

In order to achieve self-replication of the BTX tile arrays, a “seed” word is needed to begin to catalyze multiple generations of identical arrays. These researchers use a BTX seed that consisted of a sequence of seven tiles—a seven-letter “word.” To initiate the self-replication process, the seed is placed in a chemical solution, where it assembles complementary tiles to form a “daughter BTX array”-a complementary word. The daughter array is then separated from the seed by heating the solution to ~ 40°C. The process is then repeated. The daughter array binds with its complementary tiles to form a “granddaughter array,” thus achieving self-replication of the material and of the information in the seed, thus reproducing the sequence within the original seed word.

The cross-section view of the top illustration also shows two of the four helices that are formed by the lateral cohesive interactions between two BTX molecules. Credit: Paul Chaikin, Nadrian Seeman; Nature.

The excitement of the authors comes through in the abstract of their paper just published in Nature, “Considering that DNA is a functional material that can organize itself and other molecules into useful structures, our findings raise the tantalizing prospect that we may one day be able to realize self-replicating materials with various patterns or useful functions.”

Paul Chaikin, a physics professor and one of the coauthors says in the press release, “This is the first step in the process of creating artificial self-replicating materials of an arbitrary composition.” The next step is to tune the process so that many “generations” of material units are replicated.

Although the variations possible in the BTX “language” make complex structures possible, this system benefits from a major simplicity not found in the replication processes that occur within the cells: No enzymes are required and that even the DNA can be synthetic.

It seems to me that ceramic scientists are well-positioned to work with the new idea. Biomimetic materials and self-assembled monolayers have been studied for a long time. Almost daily, new articles are published about surfaces, interfaces and the nanoscale “spaces between spaces,” like the complexions between grains and grain boundaries, and are adding quickly to our understanding of how elements act when they cozy up.

Most importantly, nature already has provided the proof-of-concept with synthesis of ceramic-like components, such as bones, teeth, conch shells, etc, using a DNA-dictated process.

The paper, “Self-replication of information-bearing nanoscale patterns,” was published in the latest issue of Nature. (doi:10.1038/nature10500)

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