"These custom-built molecules can mimic the complex structures and remarkable biological properties of proteins that fight bacteria," said Tew. "The potential ability to keep surfaces and materials permanently antiseptic has significant implications and is very exciting." The new process is easier and less expensive than previous efforts at creating synthetic molecules with antibacterial properties, he said. UMass and UPenn each hold patents on the technology, which will be moving toward the marketplace within the coming years.
The team turned to nature for guidance in designing and building the new molecules, called polymers and oligomers, that act as antimicrobial agents, Tew said. "When the body is threatened by a bacterial infection, its first line of defense is a large group of defense peptides," he explained. These natural proteins are produced in our bodies all the time, said Tew, and they come into play even before white blood cells in fighting infection. There are more than 500 of these natural, bacteria-fighting peptides known.
"All cells, including bacteria, have a membrane, which acts as a parameter fence and enables the cell to closely control what enters and exits," said Tew. "These natural proteins disrupt this ‘fence,’ or membrane, causing leakage of the cell contents, leading to the death of the cell or bacterium."
These new synthetic polymers work in a similar way. The cell membrane is composed of molecules known as "phospholipids," which are amphiphilic, or have water and oil in rich regions. In bacteria, they are also negatively charged, attracting the positively charged polymers, which attach to the membrane’s surface. Once the polymers are clinging to the cell or bacterium, they punch holes in the water-and-oil membrane surrounding a cell or a microbe. "This causes the cell contents to leak out, which causes cell death," Tew said.
What is novel in the approach detailed in PNAS is that researchers focused on the overall shape of the peptides, rather than the specific chemistry, Tew said. "The antimicrobial activity of this class of peptides depends on its overall physiochemical properties, rather than the precise details of its amino acids," he noted.
Researchers hope to refine the technique in the future, which would allow the specially-designed molecules to be used in pharmaceuticals, Tew said. One area of particular focus is selectivity: that is, enabling the molecules to attack very specific cells or bacteria while leaving others unharmed. The issue does not appear to be a major obstacle, said Tew, as similar problems have been solved in other types of synthetic molecules.
Note: Gregory Tew can be reached at 413-577-1612 or gtew@polysci.umass.edu
Journal
Proceedings of the National Academy of Sciences