New DNA-Based Technique For Assembly of Nano- and Micro-sized Particles

The method, based on designed DNA shells that coat a particle's surface, can be used to manipulate the structure - and therefore the properties and potential uses - of numerous materials that may be of interest to industry. For example, such fine-tuning of materials at the molecular level promises applications in efficient energy conversion, cell-targeted systems for drug delivery, and bio-molecular sensing for environmental monitoring and medical applications.

The novel method, for which a patent application has been filed, was developed by Brookhaven researchers Mathew M. Maye, Dmytro Nykypanchuk, Daniel van der Lelie, and Oleg Gang and is described in the September 12 online edition of Small.

"Our method is unique because we attached two types of DNA with different functions to particles' surfaces," said Gang, who leads the research team. "The first type - complementary single strands of DNA - forms a double helix. The second type is non-complementary, neutral DNA, which provides a repulsive force. In contrast to previous studies in which only complementary DNA strands are attached to the particles, the addition of the repulsive force allows for regulating the size of particle clusters and the speed of their self-assembly with more precision."

"When two non-complementary DNA strands are brought together in a fixed volume that is typically occupied by one DNA strand, they compete for space," said Maye. "Thus, the DNA acts as a molecular spring, and this results in the repulsive force among particles, which we can regulate. This force allows us to more easily manipulate particles into different formations."

The researchers performed the experiments on gold nanoparticles - measuring billionths of a meter - and polystyrene (a type of plastic) microparticles - measuring millionths of a meter. These particles served as models for the possibility of using the technique with other small particles. The scientists synthesized DNA to chemically react with the particles. They controlled the assembly process by keeping the total amount of DNA constant, while varying the relative fraction of complementary and non-complementary DNA. This technique allowed for regulating assembly over a very broad range, from forming clusters consisting of millions of particles to almost keeping individual particles separate in a non-aggregating form.

"It is like adjusting molecular springs," said Nykypanchuk. "If there are too many springs, particles will 'bounce' from each other, and if there are too few springs, particles will likely stick to each other."

The method was tested separately on the nano- and micro-sized particles, and was equally successful in providing greater control than using only complementary DNA in assembling both types of particles into large or small groupings.

To determine the structure of the assembled particles and to learn how to modify them for particular uses, the researchers used transmission electron microscopy to visualize the clusters, as well as x-ray scattering at the National Synchrotron Light Source to study particles in solution, the DNA's natural environment.

Source: BNL

Scientists reveal the lifestyle evolution of wild marine bacteria
Marine bacteria in the wild organize into professions or lifestyle groups that partition many resources rather than competing for them, so that microbes with one lifestyle, such as free-floating cells, flourish in proximity with closely related microbes that may spend life attached to zooplankton or algae.
New technique yields more detailed picture of chromatin structure
University of Illinois researchers have developed a technique for imaging cells under an electron microscope that yields a sharper image of the structure of chromatin, the tightly wound bundle of genetic material and proteins that makes up the chromosomes. Their findings appear in Nature Methods.
New Method Offers Insight into Radiation Damage to DNA
A new technique for assessing the damage radiation causes to DNA indicates that the spatial arrangement of damaged sites, or lesions, is more important than the number of lesions in determining the severity of the damage. The technique, developed by scientists at the U.S. Department of Energy (DOE)'s Brookhaven National Laboratory, helps reveal why high-energy charged particles such as the heavy ions in outer space are more potentially harmful than lower-energy forms of radiation such as x-rays and gamma rays.
New technique takes a big step in examination of small structures
A team led by a Purdue University researcher has achieved images of a virus in detail two times greater than had previously been achieved. Wen Jiang, an assistant professor of biological sciences at Purdue, led a research team that used the emerging technique of single-particle electron cryomicroscopy to capture a three-dimensional image of a virus at a resolution of 4.5 angstroms.
DNA is blueprint, contractor and construction worker for new structures
DNA is the blueprint of all life, giving instruction and function to organisms ranging from simple one-celled bacteria to complex human beings. Now Northwestern University researchers report they have used DNA as the blueprint, contractor and construction worker to build a three-dimensional structure out of gold, a lifeless material.
DNA technique yields 3-D crystalline organization of nanoparticles
In an achievement some see as the "holy grail" of nanoscience, researchers at the U.S. Department of Energy's Brookhaven National Laboratory have for the first time used DNA to guide the creation of three-dimensional, ordered, crystalline structures of nanoparticles (particles with dimensions measured in billionths of a meter). The ability to engineer such 3-D structures is essential to producing functional materials that take advantage of the unique properties that may exist at the nanoscale - for example, enhanced magnetism, improved catalytic activity, or new optical properties. The research will be published in the January 31, 2008, issue of the journal Nature.
Researchers use magnetism to target cells to animal arteries
Scientists have used magnetic fields and tiny iron-bearing particles to drive healthy cells to targeted sites in blood vessels. The research, done in animals, may lead to a new method of delivering cells and genes to repair injured or diseased organs in people.
Scientists develop new tests that identify lethal prion strains quickly and accurately
One of the new in vitro tests, called the Standard Scrapie Cell Assay, measures prion infectivity levels in a highly accurate and extremely rapid way, producing results in less than two weeks. The second test, called the Cell Panel Assay, allows researchers to quickly distinguish between several prion strains in various cells lines. Using the new assays, the scientists were able to show that four different cell lines exhibited widely different responses to four different strains of the infectious protein particles.

New DNA-Based Technique For Assembly of Nano- and Micro-sized Particles

Related stories:

News discussion: