Health Scan: Tiny device diagnoses gum disease

Who would have guessed that when Star Trek's medical tricorder made its appearance in real life, its first user would be your dentist?

By JUDY SIEGEL-ITZKOVICH
teeth 88 (photo credit: )
teeth 88
(photo credit: )
Who would have guessed that when Star Trek's medical tricorder made its appearance in real life, its first user would be your dentist? According to the Proceedings of the [US] National Academy of Sciences (PNAS), a study conducted with the University of Michigan shows that a hand-held device developed at Sandia National Laboratories can determine in minutes - from just tiny sample of saliva - not only whether a patient has gum disease but how advanced it is. "The pilot study allowed us to compare our results to accepted clinical measurements," says Sandia researcher Amy Herr. "Then we could statistically validate both the periodontal disease biomarker and the new microfluidic instrument. We achieved faster and more reproducible results because we combined steps that ordinarily require manual handling by many people into a single automated device." Because the sample needed is so small, Herr sees further applications in other areas - including potentially improved diagnosis of prostate and breast cancer - as well as vaccine development. "This technology also has great promise for Sandia's efforts in homeland defense," said researcher Anup Singh. "There are ongoing efforts to use the diagnostic platform to detect biotoxins and other markers in bodily fluids." "We've filed patents," Herr added. "Our team believes Sandia's contributions could advance personalized medicine, so we're motivated to extend the limits of Sandia's lab-on-a-chip tools." A "lab on a chip" refers to an entire laboratory on a computer chip, requiring only minute amounts of material to perform automated chemical analysis. While components of the saliva-detection technique were reported earlier by Sandia, this is the first comprehensive study of Sandia's integrated method. How does the pocket-sized device work? Using a disposable lab-on-a-chip cartridge, the device makes use of a molecular sieve made out of a porous, polyacrylamide gel. The location of the sieve in the microfluidic chips is determined using photo-lithographical methods adapted from the semiconductor industry. A mild electrical current is passed through the gel, and a process called electrophoresis moves charged proteins through it. The gel permits the easy passage of smaller molecules and slows larger ones, thus quickly separating proteins in the saliva. "Biomedical researchers have suspected that changes in the amount or type of proteins present may be useful as biological markers in disease diagnosis," said Herr. "Our work with a particular enzyme in saliva supports that hypothesis. "Periodontitis can be episodic in nature," says Herr. "You need to know the stage of disease to treat the illness most effectively. The enzyme [biomarker] that we monitored decreased or stabilized if the treatment was working well." Often, owing to the time and expense, practitioners had not been able to perform extensive biochemical investigations. The work, funded by the US National Institute of Dental and Craniofacial Research, is the first application using microliters of saliva. CATCHING THE VIBES New findings at the Weizmann Institute shed light on a crucial mechanism for discerning frequencies. Dr. Itay Rousso of the structural biology department explored the mechanical properties of the tectorial membrane, testing . Using an atomic force microscope, he tested the resistance of the membrane at various points to assess how rigid it was. To his surprise, he found that one end can be up to 10 times more rigid than the other. Observation under an electron microscope revealed that this variation is due to changes in the way the protein fibers are arranged: At one end, they form a flimsy, net-like structure that allows the membrane to be flexible; on the rigid side the fibers are densely and uniformly packed. The more rigid a tectorial membrane is, the higher the frequency to which it responds.