Because of its famous structure, DNA is a practical molecule to use for nanotechnology. Learn how new materials can be constructed from the genetic material of all living organisms.

Containing the genetic information for the reproduction of life, DNA occupies a central role in biology. It may also claim top billing in the burgeoning field of nanotechnology—the study and manipulation of individual atoms and molecules to make new materials. This is because the properties that make DNA so effective as the genetic material of all living organisms also make it an ideal molecule to use for building new materials on the nanometer scale.

Since Watson and Crick figured out its structure almost 50 years ago, DNA, which stands for deoxyribonucleic acid, has touched many aspects of our lives—from genetic counseling to gene therapy to forensics. Its now well-known twisted double helix structure holds the key to materials applications.

In particular, the way that the two strands comprising DNA are held together is useful for making new materials. Hydrogen-bonded base pairs are what keeps these strands connected and the fact that these pairs are very specific and highly predictable makes DNA a logical choice for materials applications, which demand precision. For example, adenine (A) always pairs with thymine (T) and guanine (G) always goes with cytosine (C).

What’s more, materials made from DNA will possess nanoscale features because of the molecule’s naturally diminutive size.

But there’s a tricky part to building nanomaterials from DNA. Its structure is that of a linear helix axis (with “linear” meaning that it has no branches) so connecting natural DNA molecules will only result in longer linear molecules, although knots and circles may occasionally form. To become the basis of nanomaterials, DNA molecules need branch points—places where the helix axis can stick out.

Fortunately, it is feasible to have one DNA strand longer than the other, forming an overhang, otherwise known as a “sticky end.” By using such sticky ends, genetic engineers can hook double helices together and build materials.

And sticky ends represent an effective way to form materials because of how they cohere. For one thing, the bind they form is strong. Also, their cohesion process is straightforward and controllable, as they stick together in a predictable fashion. And third, they form specific intermolecular structures so engineers don’t have to conduct new experiments to ascertain the cohesive system’s local geometry. What’s more, sticky ends can form a highly diverse variety of sequences.

But what can we do with DNA-based materials? Such materials may be able to form nanosized crystalline cages, in which other biological macromolecules can be housed for analysis. Also, with these crystalline arrays acting as cages, genetic engineers can manipulate components of molecular electronic devices with nanometer-scale precision. Thus, a simple structure like a crystalline cage can eventually pave the way for the production of nanosized robotics and extremely smart materials, which can be programmed to respond to certain stimuli.

In fact, structural DNA nanotechnology has already claimed several successes. The first was the creation of a three-connected DNA molecule, resembling a cube. Also, DNA nanotechnology has been able to produce two-dimensional periodic arrays with distinct features. And third, it has been helpful in making nanomechanical devices, which need to be placed in an array matrix in order to be the basis for nanorobotics.

There is still substantial development work to be done, however, before the potential of DNA nanotechnology is fully realized. Scientists have to improve their array-making capabilities and learn how to incorporate other types of molecules into DNA arrays to inch closer to the goal of arranging nanoelectronic circuits. Eventually, structural DNA nanotechnology must not only utilize the central molecules of life but also build upon their intrinsic power.

Source: DNA Nanotechnology
Nadrian C. Seeman
Materials Today, Jan. 2003
http://www.materialstoday.com