The UI team created a synthetic probe with two unique features. On one end is a molecule that gives off light under certain conditions. On the other end is another molecule that blocks that light. In other words, the particle, as designed, cancels itself out, leaving itself undetectable inside the body.
This is important due to what staph bacteria will do to the particle. In tests, nucleases (or enzymes) produced by the staph bacteria cleave the particles, like a warrior wielding a sword. (Why it does this is unclear, but scientists believe it's a clever way for staph, which can't move by itself, to spread beyond the molasses-like environment created when DNA leaks from infected, dying cells.) In any event, when staph cleaves the probe, it separates the light-emitting molecule from the light-blocking molecule, which then drifts too far away to block light. And, so with the right equipment, doctors would be able to see the light-emitting molecules and know that staph are raging there.
Outfitting such particles is not altogether new, but McNamara and his colleagues produced a probe that lasts longerby several hours longer for certain types.
"We designed a tracking system that specifically identifies bacterial body localization in less than one hour," says Hernandez, a Colombian who for years has been working on probes to detect harmful bacteria.
Just as important, the UI probe has been chemically modified so that it's shredded only by the staph bacteria's nuclease and not by a nuclease secreted by normal, healthy cells. The team further tested the probe in mice and human serum and report that it performed as expected.
"That's the central idea, the underlying concept of our approach," says McNamara, whose primary appointment is in the Carver College of Medicine. "If the probe gets cleaved by serum nucleases, then our probe would be lit up all over the bloodstream. But since it's split only by staph nuclease
|Contact: Richard Lewis|
University of Iowa