Instant Diagnostics on the Horizon

Originally Published MDDI April 2005

R&D DIGEST

Maria Fontanazza

A handheld device that detects diseases from a saliva sample could open the door to a faster way of testing for gum disease and other conditions. A multicenter research team has incorporated lab-on-a-chip technology with an immunoassay process. The device, which analyzes biomarkers associated with certain diseases, could reveal critical information in minutes and eliminate the need to send samples to a lab.

“The future use of these devices is almost unlimited,” says Mark Burns, PhD, a professor at the University of Michigan's College of Engineering in Ann Arbor, a partner in the research. “Just as computer chips are ubiquitous today, so will microfabricated chemical analysis systems be in the future.”

Weighing about 5 lb, the device currently analyzes saliva for gum disease in healthy patients. The team, which also includes scholars from Sandia National Laboratories (Livermore, CA), Cornell University (Ithaca, NY), and the University of Michigan's School of Dentistry (Ann Arbor), anticipates testing diseased samples in upcoming months.

“The next step in the process is to test our technology for its ability to detect biomarkers in saliva and gingival crevicular fluid from diseased patients,” says Anup Singh, principal member of the technical staff at Sandia Labs. “We also need to compare the results obtained from our chips to conventional assays that are currently used.”

However, using saliva also presents a challenge. It is greatly affected by the method of collection and the prevailing environment in the mouth, says Singh. “It will be imperative to standardize saliva collection and treatment before our device can provide reproducible results.”

During the process, antibodies particular to biomarkers of interest, such as gum disease, are tagged with fluorescent dye and mixed with a saliva or blood sample. After the biomarkers stick to the antibodies, the mix is injected into a microchip. With the help of an electric field, it passes through a microchannel, and molecules are arranged based on their electrical charges and sizes.

If biomarkers specific to the disease are in the sample, the lab-on-a-chip assay separates the antibodies. Based on whether or not the sample has biomarkers above a particular level, the doctor can deduce whether the patient will be prone to the disease.

The technology has the potential to detect serious diseases, such as heart disease and cancer. And since it can also work with blood samples, other medical applications could be developed.

“While this is preliminary research, we hope to have a prototype available [that can detect] gum disease,” says Burns. “And extending the technology to other diseases poses very few technical challenges. Our group in Michigan is working on a variety of devices, including a chip to measure the viscosity of blood and one to detect and subtype the influenza virus.”

Harold Craighead, PhD, a professor at Cornell's School of Applied and Engineering Physics, agrees. “The basic structure and approach can be expanded to other fluids and diseases,” he says. “The idea of having a miniaturized microfluidic-based
technique has a broad applicability.” However, he says, working with saliva is a good place to start, because the sampling procedure is noninvasive.

According to Singh, the researchers want to make the chips compatible with as many bodily fluids as possible. Future research will also test their applicability to urine and tears.

The National Institutes of Health (Bethesda, MD) is funding the research.

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