Professor and Department Chair
PhD, Theoretical Solid State Physics
Ravi Pandey was trying to determine if nanotubes would work as taxis to deliver chemotherapy drugs to tumors. Then he discovered something quirky about DNA that could revolutionize gene-sequencing technology.
Chemotherapy is a tried-and-true cancer therapy, but for many patients, the drugs are so toxic that the cure is worse than the disease. So, rather than dosing the entire person with healing poisons, scientists want to shuttle those drugs directly to the tumor, with carbon nanotubes serving as the shuttle.
First, however, they want to make sure they aren't making things worse. Nanotubes are, as their name suggests, incredibly tiny, not much bigger than a strand of DNA.
Common prudence would suggest that, before injecting them into people, you would want to make sure they don't cause more problems than they solve.
Pandey, chair of Tech's physics department, and his team wanted to find out if carbon nanotubes react with the bases of DNA—adenine, cytosine, guanine, and thymine, or ACGT for short. If those bases are not reactive, then carbon nanotubes are probably safe.
So, they went down to the sub-molecular level, to the clouds of electrons that hover over atoms and molecules. When molecules and atoms get close to each other, they deform that electron cloud. Some deform more than others, a quality known as polarizability.
If the polarizability is really significant, substances tend to bind strongly to each other. When Pandey's group calculated the polarizability of A, C, G, and T vis-a-vis carbon nanotubes, however, he got good news: low binding, meaning that carbon nanotubes had crossed one bridge on the path to a better way to deliver chemotherapy drugs.
But Pandey noticed something else. With respect to the carbon nanotube, they found slight differences in each of DNA's four bases.
"They are subtle, but there are differences in the binding energy that come from polarizability," says Pandey. "At one of our conferences, we sat down at dinner one evening and asked, ‘Could we apply these differences somehow?'"
The answer was an emphatic "maybe." Maybe you could sequence DNA by somehow measuring the binding energy of each of the ACGT bases, one after another. "It was a little hunch, a napkin decision," he says.
Back at the University, Pandey and his team began to turn the back-of-the-napkin maybe into a yes, with collaboration with Trinity College, the Army Research Lab, and Uppsala University.
Using computer modeling, they developed a new way to sequence DNA that could be far easier and cheaper than current methods.
"You just pull strands of DNA through a carbon nanotube membrane with an electric current going through it," Pandey says. It's a little more complicated than that, but tiny changes in the voltage signal which base is which, in perfect order, along the famous double helix.
Present sequencing methods are expensive and slow, and Pandey hopes that their breakthrough might someday revolutionize the technology.
"This is only possible because the scale of materials has gone down to the nano-level,"
says Pandey. "We're using quantum mechanics to understand biological processes. It's the fusion of biology and physics—a whole new world."