"When we wash away the solution and test the nanotube transistors again, the change in what we measure tells us that how much of the antigen has bound," Johnson said. "And we see the relationship we expect to see, in that the more antigen there was in the solution, the bigger the change in the signal."
The smallest concentration the nanotube devices could detect was four nanograms of protein per milliliter of solution.
"This sensitivity is more than sufficient to detect the Lyme disease bacterium in the blood of recently-infected patients and may be sufficient to detect the bacterium in fluids of patients that have received inadequate treatment," Brisson said.
"We really want the protein we are looking to detect to bind as close to the nanotube as possible, as that is what increases the strength of the electrical signal," Johnson said. "Developing a smaller, minimal version of the antibody what we call a single chain variable fragment would be a next step.
"Based on our previous work with single chain variable fragments of other antibodies, this would probably make such a device about a thousand times more sensitive."
The researchers suggested that, given the flexibility of their technique for attaching different biological structure, eventual diagnostic tools could incorporate multiple antibodies, each detecting a different protein from the Lyme bacterium. Such a setup would improve accuracy and cut down on the possibility of false-positive diagnoses.
"If we were to do this type of test on a person's blood now, however, we would say the person has the disease," Johnson said. "The first thought is that if you detect any protein coming from the Lyme organism in your blood, you are infected and should get
|Contact: Evan Lerner|
University of Pennsylvania