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RESEARCH PROFILES Biosensor to help Crohn’s disease patients
SYLVIA DAUNERT
whether the ketonic bodies in her daughThe investigators are now gearing up Almost nothing is available to help pater’s breath were derived from acylhoto take the whole-cell biosensing system tients with Crohn’s disease manage their moserine lactones (AHLs), molecules through clinical trials. They are interested incurable and chronic illness. Sylvia used by Gram-negative bacteria to “talk” in studying whether a direct correlation Daunert of the University of Kentucky to one another. “I thought, let’s see exists between bacterial infection and knows that all too well—her daughter what her AHL levels are like. I asked flare-ups in Crohn’s disease. Daunert has the disease, which causes painful, Shashi, ‘Do you think I’m crazy?’ He emphasizes that the basis for a successful often unbearable, inflammation of the said, ‘No, I think you’re right!’” says analysis will be a record of each patient’s gastrointestinal tract. Daunert. baseline levels of AHLs and other key Some evidence suggests that bacteria chemicals involved (e.g., are involved in diseases the oligopeptides used by of chronic inflammaCell–cell communication Gram-positive bacteria for tion. So Daunert, along cell–cell communication). with her colleagues, She is emphatic about have developed a the baseline readings bebiosensor, described in cause, while developing the November 15 issue the biosensor, she was of Analytical Chemistry struck by the variability in (pp 7603–7609), that LuxR Lu x R AHLs in people of differeavesdrops on the ent ethnic backgrounds. “chatter” among bacte“We were doing the saliria. The sensor could AHL AHL A H L A H L va samples, and the volsomeday let patients unteers were my students. with Crohn’s monitor (a) In quorum sensing, Gram-negative bacteria produce AHLs that freely diffuse There were different the status of the disease into the extracellular medium. (b) When a critical concentration of AHLs is reached, kinds of readings from by checking their bactecell–cell communication occurs, and AHL binds to its regulatory protein, LuxR. my Chinese students, rial levels. The result is the increased production of AHLs and activation of target genes. from my Greek students, Two observations They needed an analytical method to from my Indian students,” she says. “Demade during her daughter’s relapses got quantify AHL levels in clinical samples, pending on your ethnic background and Daunert and her daughter’s physician, so they turned to whole-cell biosensors. on your eating habits, you will have difHarohalli Shashidhar (whom they call ferent types of microflora in your intesShashi), thinking about bacteria and the The investigators used genetically engineered E. coli cells to produce luciferase tine. There is no question about that. way they communicate with one anothas a function of AHL concentration. The [So] you need to have a baseline reading er, a phenomenon known as quorum sensing. “One time when she was hospi- intensity of the bioluminescent signal was from each person.” Besides the clinical trials, the investitalized, we noticed how antibiotics were directly proportional to the AHL congators are working on creating easy-toreally helping her get better. Since then, centration. Daunert and colleagues determined use formats of the biosensor. One apwhenever she was getting very sick, that the biosensor could detect N-butyryl- proach is to convert the current test-tube Shashi would either give her antibiotics setup into a paper-strip one. The ultiorally or take her to the hospital to give DL-homoserine lactone and N-hexanoylmate goal would be to develop a simple her antibiotics through IV. Antibiotics DL-homoserine lactone concentrations test where “patients look at the levels of helped her and were always the first opas low as 1 10 –9 M over a dynamic the signaling molecules on a daily basis. tion before we tried medications, like range of 4 orders of magnitude. They When they see the molecules starting to steroids, that had quite a few undesiralso applied the biosensor to the detecchange, they can take medication and able side effects,” says Daunert. tion of AHLs in saliva and stool. Some avoid going to the hospital,” says Also, during one of the early episodes sample prep was necessary—saliva had Daunert. of her daughter’s illness, Daunert was to be centrifuged to remove viscous As for Daunert’s daughter, she has struck by something else. “I noticed that components and debris, and the stool started as a premed freshman at Princeher breath smelled sweet,” says Daunert. samples required diluting—but the bioton University this year. Daunert says, It reminded Daunert of the sweet smell sensor worked just as well for the bioof ketonic bodies that diabetics have in logical samples as it did for the solutions “She never lets Crohn’s ruin her life.” a —Rajendrani Mukhopadhyay their breath. She started to wonder of AHLs. 7910
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