Carnegie Mellon University scientists have married bright fluorescent dye molecules with DNA nanostructure templates to make nanosized fluorescent labels that hold considerable promise for studying fundamental chemical and biochemical reactions in single molecules or cells. The work, published online Jan. 26 in "The Journal of the American Chemical Society,” improves the sensitivity for fluorescence-based imaging and medical diagnostics.
"Our DNA nanotags offer unprecedented densities of fluorescent dyes and, thus, the potential for extremely bright fluorescent labels,” said graduate student Andrea Benvin, who developed the nanotags in the laboratory of Bruce Armitage, associate professor of chemistry in the Mellon College of Science (MCS) at Carnegie Mellon. "We’ve put it all into a very small package, which will allow us to detect molecules with great sensitivity without interfering with the biological processes we are trying to understand."
The high brightness of the nanotags should be of great help in detecting rare cancer cells within tissue biopsies, for example, which is important in determining whether treatments have been successful or if recurrence is likely, according to Armitage. In addition, DNA nanotags offer the opportunity to perform multicolor experiments. This feature is extremely useful for imaging applications, Armitage says, because the multiple colors can be seen simultaneously, requiring only one experiment using one laser and one fluorescence-imaging machine.
"For example, two different populations of cells, one healthy and the other cancerous, could be distinguished based on labeling them with different color fluorescent nanotags," Armitage said.
Benvin, Armitage and colleagues at Carnegie Mellon’s Molecular Biosensor and Imaging Center modeled their DNA nanotags on the structure of phycobiliproteins. Found in certain types of algae, such as the red and blue algae in fresh and marine waters, these proteins contain multiple, fluorescent pigments that work together to absorb light energy that is then transferred to chlorophyll, where it is used for photosynthesis. The Carnegie Mellon team has mimicked this efficient light-harvesting process in the design of their DNA nanotags to create incredibly bright, fluorescent labels.
"The primary advantages of our system are the simplicity of its design combined with the ease with which the fluorescence brightness and color can be tuned," Armitage said.
To achieve greater brightness, the Carnegie Mellon team assembled well-defined nanostructured DNA templates that bind multiple fluorescent dye molecules between base pairs in the DNA helix (see image). This arrangement keeps dyes far enough away from each other to avoid canceling out each other’s fluorescence. The DNA templates can also be modified to bind to other molecules or to the surface of a cell of interest. The innovative design creates nanotags with large light-harvesting capabilities and very high light-emission (fluorescence) intensities. Because the DNA can accommodate one dye for every two base pairs, a DNA nanostructure with 30 base pairs can bind up to 15 fluorescent dye molecules. The resulting dye-DNA complexes are approximately 15 times brighter than an individual dye molecule. And they can be made even brighter by simply increasing the number of base pairs in the DNA nanostructure.
Multicolor experiments are possible because the DNA nanotags contain "light-harvesting" dyes within the DNA helix that are excited by one wavelength of light and then transfer that excitation energy to "light-emitting" dyes on the nanotag’s surface. The light-emitting dyes can fluoresce at a different color from the light-harvesting dye. For example, one type of DNA nanotag can act as an antenna that efficiently harvests blue light and transfers that light energy to another dye within the nanostructure. The second dye then emits orange, red or even infrared light. Changing the light-harvesting dyes allows even more variation in the fluorescence color, Armitage said.
The nanotags are easily assembled by mixing commercially available DNA strands and fluorescent dyes. And while the work described by the Carnegie Mellon team relied on a relatively simple two-dimensional DNA nanostructure, Armitage notes that the rapidly growing field of DNA nanotechnology is generating increasingly intricate three-dimensional nanostructures that should lead to further improvements in brightness.
"We really feel that this is the tip of the iceberg and that nanotags 100 times brighter than existing labels can be developed in any color," he said.
Lauren Ward | EurekAlert!
Fish recognize their prey by electric colors
13.11.2018 | Rheinische Friedrich-Wilhelms-Universität Bonn
The dawn of a new era for genebanks - molecular characterisation of an entire genebank collection
13.11.2018 | Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung
Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.
Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure
Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...
Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly
The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...
09.11.2018 | Event News
06.11.2018 | Event News
23.10.2018 | Event News
13.11.2018 | Life Sciences
13.11.2018 | Life Sciences
13.11.2018 | Awards Funding