Light-Activated Bug Killers

A novel class of light-activated antimicrobial agents—hollow capsules composed of conjugated polyelectrolytes—can efficiently kill drug-resistant, gram-negative bacteria (ACS Appl. Mater. Interfaces, DOI: 10.1021/am800096q). The proliferation of these bacteria is a worldwide concern and is prompting the design of new agents that could be useful in hospitals and in homes. Kirk S. Schanze of the University of Florida, David G. Whitten of the University of New Mexico, and colleagues write that the photoactive capsules attract, trap, and kill bacteria much like a Roach Motel takes care of cockroaches. The researchers fabricated the capsules by applying alternating layers of anionic and cationic phenylene-ethynylene materials onto manganese carbonate template particles, followed by dissolution of the template. In lab tests, more than 95% of Cobetia marina and Pseudomonas aeruginosa died when each of the pathogenic bacteria was mixed with a suspension of capsules and exposed to white light for up to one hour. The researchers speculate that the antimicrobial activity ultimately results from the generation of singlet oxygen and other reactive oxygen species initiated when the conjugated polyelectrolytes absorb light. Schanze adds that it should be possible to make coatings or directly modify surfaces with the capsules.