McGowan Institute researchers have synthesized a simple molecule that not only produces perfectly uniform, self-assembled nanotubes but creates what they report as the first “nanocarpet,” whereby these nanotubes organize themselves into an expanse of upright clusters that when magnified a million times resemble the fibers of a shag rug. Moreover, unlike other nanotube structures, these tubes display sensitivity to different agents by changing color and can be trained to kill bacteria, such as E. coli, with just a jab to its cell membrane.
How a single-step synthesis of a hydrocarbon and a simple salt compound produced these unique nanotube structures with antimicrobial capability is described in a paper posted on the Web site for the Journal of the American Chemical Society . “In these nanotube structures, we have created a material that has the ability to sense their environment. The work is an outgrowth of our interest in developing materials that both sense and decontaminate chemical or biological weapons,” said senior author Alan Russell, Ph.D.
Figure: SEM images of the formation of nanotubes and nanocarpets: (A) nanotubes
and lamellar structures formed from the intermediates of quaternization; (B)
lamellar structures of the bromine salt of 2; © linear nanotubes and one
branched nanotube from compound 3 showing the monodispersity of the diameters;
(D) nanocarpet; (E) front view of the nanocarpet; (F) side view of the nanocarpet.
“To our knowledge, the remarkable self-assembly of this inexpensive and simple lipid is unprecedented and represents an important step toward rational design of bioactive nanostructures. In addition, because they form within hours under room-temperature conditions, the significant costs of synthesizing carbon nanotubes can be reduced,” explained first author Sang Beom Lee, Ph.D., research assistant professor of bioengineering in the School of Engineering.
The most critical performance tests, say the researchers, were those involving E. coli, which were conducted to assess the material’s interactions with living cells. In the presence of E. coli, some strains of which are food-borne pathogens, the nanotubes turned shades of red and pink. Moreover, with the aid of an electron microscope, the researchers observed the tubes piercing the membranes of the bacteria like a needle being inserted into the cell. Both the polymerized (those that can change color) and the unpolymerized nanotube structures were effective antimicrobials, completely killing all the E. coli within an hour’s time.
“We are very encouraged by these results and we will be continuing our investigations of this novel material in collaboration with our colleagues at the University of Pittsburgh and the U.S. Army Research Office,” added Dr. Russell.
In addition to Drs. Russell and Lee, other authors, all from the University of Pittsburgh, are Richard Koepsel, Ph.D., department of chemical and petroleum engineering, School of Engineering; Donna B. Stolz, Ph.D., Center for Biologic Imaging, School of Medicine; and Heidi E. Warriner, Ph.D., department of chemistry, School of Arts and Sciences.