Plastics vs the 'superbug'

Researchers have found that a specially designed polycarbonate molecule holds promise in the fight against superbugs, microbes that resist a range of conventional drugs.

Scientists at IBM and Singapore's Institute of Bioengineering and Nanotechnology found the new polymer can kill five deadly types of bacteria resistant to multiple drugs without side effects. Unlike other approaches to polymer-based anti-microbials, this new polymer does not appear toxic, is biodegradable and attacks a broad selection of bacteria.

"This is another example of how to exploit polymer science to bring it to medicine," James Hedrick told Plastics News in a phone interview.

Hedrick led the team at IBM's Almaden, Calif., laboratories. Researchers there and in Singapore collaborated on the project. Hedrick has been leading several research projects exploring exotic uses for new polymers. In 2016, IBM researchers and other scientists discovered polymers that can attack viruses.

The new research "rounds out our ability to someday treat a spectrum of infectious diseases with a single, new type of mechanism without the onset of resistance," Hedrick stated in a March 6 news release from Singapore's Agency for Science, Technology and Research.

The research was reported by the IBM and IBN teams March 5 in the peer-reviewed journal Nature Communications.

Researchers created a polycarbonate with a guanidinium unit attached. Guanidinium is an easily synthesized molecule containing three nitrogen atoms and six hydrogen atoms. It has limited medical usefulness when used in its simplest forms.

Hedrick said the new polymer is a white powder, soluble in water, that degrades into non-toxic compounds like organic acids and alcohols. It mimics natural antimicrobials based on peptides. It kills bacteria by first attaching to the bacteria cell membrane. It is then transported across the membrane into the cytoplasm, where it causes proteins and genetic material to precipitate. Cell death ensues.

Researchers tested the new polymer on mice infected with five hard-to-treat bacteria that can cause infections in hospital that lead to septic shock and multiple organ failure. Tests showed the bacteria were no longer active in the mice, which showed no toxicity. Further tests showed bacteria did not develop resistance to the polymer.

"We have demonstrated the first example of a biodegradable synthetic macromolecule with broad-spectrum antimicrobial activity in mice, unique killing mechanism and no toxicity," said Yi Yan Yang, group leader at IBN, in a news release. "Once the polymer finishes its job of killing the bacteria, it will be naturally degraded after three days and will not remain in the body."

Hedrick's interest in the work began when he developed a staphylococcus-type infection in the hospital after surgery. He praised the potential that polymers exhibit in such applications.

"In the 20th century, polymers were developed. In the 21st century, polymers are experiencing a renaissance," Hedrick said.