18 July 2012
Synthetic pores, inspired by nature, mimic critical features of cellular ion channels, which restrict the types of materials allowed to enter human cells.
The pores the scientists built are permeable to potassium ions and water, but not to other ions such as sodium and lithium ions.
This kind of extreme selectivity, while prominent in nature, is unprecedented for a synthetic structure, says University at Buffalo chemistry professor Bing Gong, who led the study published in Nature Communications.
The project’s success lays the foundation for an array of exciting new technologies. In the future, scientists could use such highly discerning pores to purify water, kill tumors, or otherwise treat disease by regulating the substances inside of cells.
“The idea for this research originated from the biological world, from our hope to mimic biological structures, and we were thrilled by the results,” Gong says. “We have created the first quantitatively confirmed synthetic water channel. Few synthetic pores are so highly selective.”
To create the synthetic pores, researchers developed a method to force doughnut-shaped molecules called rigid macrocycles to pile on top of one another. The scientists then stitched these stacks of molecules together using hydrogen bonding. The resulting structure was a nanotube with a pore less than a nanometer in diameter.
“This nanotube can be viewed as a stack of many, many rings,” says Xiao Cheng Zeng, professor of chemistry at the University of Nebraska-Lincoln and one of the study’s senior authors. “The rings come together through a process called self-assembly, and it’s very precise. It’s the first synthetic nanotube that has a very uniform diameter. It’s actually a sub-nanometer tube. It’s about 8.8 angstroms.” (One angstrom is one-10th of a nanometer, which is one-billionth of a meter.)
The next step in the research is to tune the structure of the pores to allow different materials to selectively pass through, and to figure out what qualities govern the transport of materials through the pores, Gong says.
The research was funded largely by the National Science Foundation, and X-ray work was done at the Advanced Photon Source at Argonne National Laboratory.