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Doctors worldwide are fighting a war against antibiotic-resistant bacteria, which can cause serious infections in hospital patients with low immune systems. X. Nancy Xu, Old Dominion University associate professor of chemistry and biochemistry and two of her graduate students Sophia Kyriacou and Robert Jeffers, have synthesized "nanoprobes" and discovered that they are capable of inhibiting the cell growth of the bacteria, pseudomonas aeruginosa. Their research was published in the journals, Nano Letters and Biochemistry and is currently under review by the U.S. Patent Office.

"This is not science fiction or hype," Xu said. "We are ahead of the game with single-molecule detection and using nanoprobes not only as an unconventional drug, but as a way to understand why bacteria behave the way they do."

The bacteria P. aeruginosa, can be found in most environments, but in hospitals it causes dangerous infections, especially in those suffering from severe burns, cancer, AIDS and cystic fibrosis as well as patients undergoing transplants. "Doctors use higher and higher doses of antibiotics in trying to kill bacteria that is multidrug-resistant, which only causes the bacteria to become more resistant," Xu said. "Pharmaceutical companies design more and more antibiotics to treat the infections, which only leads to more and more strains of bacteria that are drug-resistant," she continued. These infections are impossible to eradicate in part because of their intrinsic resistance to the wide spectra of structurally and functionally unrelated antibiotics, she added.

"In our study, we used silver- enhanced gold nanoparticles as nanoprobes in low concentrations to view single bacterial cells in real-time," Xu said. "Eventually, when the concentration of nanoparticles is increased, the bacteria basically run out of space to accommodate nanoparticles and hence stop growing. We envision that these nanoprobes could be used as a cream or a disinfectant that could be applied topically to inhibit bacterial growth. Furthermore, these nanoparticles can be used to study other important membrane transport mechanisms, such as multi-drug resistance in tumor cells, for exploring the possibility of effective and low side-effect chemotherapy and radiotherapy."

Xu's research team developed single nanoparticle optic assays and single living cell imaging to study the real-time sized transformation of cell wall and membrane permeability in individual living cells at nanometer sized resolution and millisecond temporal resolution. Supported by the National Institutes of Health, the group is also studying how the bacteria become resistant to antibiotics, probing their metabolic capability, environmental versatility and ability to cause disease.

The group is also using the technology to better understand radiotherapy's effect on brain tumors and surrounding cells, to better understand heart disease and to detect cancer earlier.

Xu, who joined Old Dominion in 1998, received her doctorate in analytical chemistry from the University of Mississippi and was a postdoctoral fellow at University of Texas at Austin and the Department of Energy Ames Lab.

This article was posted on: May 12, 2004

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