Gum disease detector shows its teeth

A University of Michigan study has proved a Sandia National Laboratories handheld device can determine from a sample of saliva whether a patient has gum disease and how advanced it is.

‘The gold standard for any medical test is when instruments are used to examine human patients,’ said Sandia researcher Amy Herr. ‘The pilot study allowed us to compare our results to accepted clinical measurements. 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 time-consuming manual handling by many people, into a single automated device.’

Because the amount of sample fluid needed for testing is so small, Herr sees further applications in other disease areas. These include potentially improved diagnosis of prostate and breast cancer as well as rapid measurements of serum in animal models employed in vaccine development research.

‘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 current work with a particular enzyme in saliva supports that hypothesis regarding periodontal disease.’

The pocket-sized device measures the state of biomarkers to determine how much the disease has been set back. Its progress may be hard to detect, advancing or retreating without showing any signs.

‘Periodontitis can be episodic in nature,’ said Herr. ‘You need to know the stage of disease progression to diagnose and treat the illness most effectively. The biomarker enzyme that we monitored decreased or stabilised if the treatment was working well.’

Often, owing to the time and expense involved, practitioners formerly had not been able to perform extensive biochemical investigations.

Unlike Sandia’s MicroChemLab lab-on-a-chip which reports multiple protein signatures in fluids of interest, the new device is designed to quantify the amount of a specific protein or panel of proteins present in particular biological fluids.

Using a disposable lab-on-a-chip cartridge, the device uses a molecular sieve made out of a polyacrylamide gel. The location of the sieve in the microfluidic chips is determined using photo-lithographical methods adapted from the semiconductor industry. The gel is porous, with very small openings.

A low electrical current is passed through the gel and a process called electrophoresis moves charged proteins through it. The gel has a gelatine-like consistency and, by permitting the easy passage of smaller molecules and slowing the passage of larger ones, quickly separates proteins contained in the saliva.

Prior to this separation, the proteins are brought into contact with specific antibodies chosen on their ability to bind to the biomarkers. The antibodies are pre-labelled with fluorescent molecules attached to them. Interrogation by laser of these combined molecules determines the amount of biomarker present, indicating the degree of periodontitis.