Chipped teeth, or how to diagnose periodontal disease using a microchip

Did you ever imagine there would come a time when you could self-diagnose major diseases at home, much like using a home pregnancy test? That day has come one step closer, according to an article in the Proceedings of the National Academy of Sciences (Herr et al, doi:10.1073/pnas.0607254104). It all happened when an oral research and dentistry group at the University of Michigan combined forces with the Biosystems Research Department at Sandia National Laboratories to develop a microfluidics chip that can detect dental disease.

Point-of-care (POC) diagnostics are already part of our every day live. Home pregnancy tests, blood glucose monitors, and sexually transmitted diseases kits are globally used thanks to their fast results. POC tools measure characteristics symptomatic of a particular pathology, known as biomarkers. For example, a high cholesterol level combined with increased blood pressure is indicative of cardiovascular disease.
So how does this chip really work? It detects periodontitis, a chronic inflammatory oral disease caused by bacterial plaque depositions on our teeth. The microchip uses a salivary protein, called matrix metalloproteinase-8 (MM-8), as its biomarker. First, a fluorescent antibody, able bind to MM-8, is loaded onto a porous polyacrylamide gel that forms part of the chip. A mere 20 microlitres of saliva provided by a patient is then poured into the device. MM-8 present in the sample complexes with the antibody, becoming fluorescent itself. An electric potential is subsequently applied to the gel. Charged molecules will separate in bands depending on their size and charge; biochemists routinely use this technique, known as electrophoresis. The distinct bands can finally be identified by fluorescence and the amount of MM-8/antibody fluorescent complex is quantified against standards also present in the gel. High concentrations of MM-8 in saliva are thus indicative of periodontal disease.

The oral diagnostics area is so hot right now that the New York Academy of Sciences is published an entire volume on it (Oral Based Diagnostics, Volume 1098, March 2007, ISBN 1-57331-661-X) with articles from leading scientists, including researchers at the USA National Institute of Health. Tests based on blood have traditionally been considered to convey more information on systemic diseases, like cancer and HIV. However, advances such as this periodontitis chip guide us towards a future where commercially available kits could provide results rapidly, cost-effectively and chiefly from minute sample volumes.