Arrays of nanofibers able to deliver genetic material to cells quickly and efficiently have researchers at Oak Ridge National Laboratory excited about potential applications for drug delivery, gene therapy, crop engineering and environmental monitoring.
Tim McKnight of ORNL's Engineering Science and Technology Division and researchers from several other laboratory divisions and the University of Tennessee are working to advance the science of micro-injection. The work builds upon the group's success with fabricating carbon nanofibers, which are tiny needles that provide a new approach to genetic manipulation of cells and biological organisms.
"By using an array of millions of carbon nanofibers that can be grown on various platforms - or substrates - we can streamline a proven technique for altering the DNA content of a cell," McKnight said.
That proven technique, micro-injection, involves introducing genetic material, DNA, directly into a cell's nucleus. This allows researchers to genetically alter the attributes of a cell and to exploit the cell to perform desired functions such as to produce a pharmaceutically active compound to grow under adverse conditions or to detect environmental hazards.
The group's technique, which has grown from a project funded by ORNL seed money in the spring of 2002, allows for highly controlled rapid delivery of genetic material into large numbers of cells.
"While we have focused predominantly on mammalian cells, the parallel micro-injection-based technique should be quite transferable to a wide variety of cell types, including those with rugged cell walls such as plants and bacteria," McKnight said.
Of particular interest is the fact that the new method allows researchers to attach DNA to the nanofibers. When they insert these nanofibers into cells, the DNA can be used to program the cell to produce new proteins, but it is not free to move around within the cell. As such, it has a less likely chance of inserting into the cell's chromosomes or being segregated to daughter cells when the cell divides. Mike Simpson of the group has somewhat paradoxically called this a "non-inheritable genetic modification."
This non-inheritable tethered DNA method has exciting potential, McKnight said. For instance, it may address some of the concerns related to genetically modified organisms.
Already, scientists are using these organisms for a variety of agricultural and environmental applications. A well-known example is golden rice, engineered for improved nutritional value to help feed the world's expanding population. Locally, the group's collaborators at the University of Tennessee's Center for Environmental Biotechnology use genetically engineered bacteria immobilized to a sensing platform to provide highly sensitive warning systems against environmental toxins.
In the areas of agricultural and environmental applications, some people are concerned about the potential of uncontrolled release of genetically modified organisms to the environment. However, the tethered DNA approach might significantly reduce the risk of such release. While the organisms might escape from the system, the nanofibers hold the modifying DNA captive.
"So when or if the organisms become detached from the nanofibers, they would no longer have access to the modifying DNA and therefore should revert to their normal genetic makeup," McKnight said.
In addition to investigating nanofiber platforms for DNA delivery, the group is involved in a $1.7 million three-year effort to apply nanofiber devices for high-resolution molecular imaging of cells and tissue. The sponsor, the National Institutes of Health, is specifically interested in molecular imaging because such information can provide insight into disease.
ORNL also is beginning a collaboration with the Institute of Paper Science and Technology. The project is aimed at using these techniques for genetic manipulation of loblolly pine, the most important wood pulp species in the United States. In addition, ORNL is pursuing the technique for transdermal drug or gene delivery, whereby a small nanofiber-based chip could be attached to the skin and would inject the drug or genes into the body.
The groups' research on nanostructures was published recently in the Institute of Physics Publishing's Nanotechnology (April 9). Co-authors are Anatoli Melechko of the University of Tennessee and Guy Griffin, Michael Guillorn, Vladimir Merkulov, Francisco Serna, Dale Hensley, Mitch Doktycz, Doug Lowndes and Mike Simpson of ORNL.