Lab on a chip finds periodontal bacteria

Caren B. Les, caren.les@photonics.com

Periodontitis is no fun. It’s a gum infection that can cause pain and bleeding, and rob you of your teeth; it has even been linked to increased risk of heart attack or stroke. But an optics-based diagnostic platform could help dentists rapidly identify any periodontitis-causing pathogens that may be lurking around your teeth, enabling faster treatment.

Current detection methods involve time-consuming off-site lab testing – and carry the risk of killing the bacteria samples.

“Until now, analysis took around four to six hours,” said Dirk Kuhlmeier, a scientist at the Fraunhofer Institute for Cell Therapy and Immunology IZI in Leipzig, Germany. Kuhlmeier, in collaboration with the companies BECIT GmbH and ERT-Optik, developed a prototype mobile lab-on-a-chip module called ParoChip – designed to speedily identify 11 of the most relevant periodontitis pathogens.

An optics-based lab-on-a-chip module could provide dentists with a speedy way to identify periodontal bacteria. Sterile paper points are used to remove bacteria from the tooth for testing. ©Fraunhofer IZI.

“With ParoChip, it takes less than 30 minutes,” Kuhlmeier added. “This means it’s possible to analyze a large number of samples in a short amount of time. Using ParoChip does away with many of the manual steps that are a necessary part of current bacteria tests.”

The platform for the automated, noncontact process consists of a disk-shaped microfluidic card that is about 6 cm in diameter. There are 11 chambers on the card, each featuring a reagent for one of 11 periodontal pathogens. A sample is taken from the patient using a sterile paper point; the bacteria are removed from the point, and their isolated DNA is injected into the reaction chambers.

The total number of bacteria is determined in an additional chamber via polymerase chain reaction (PCR). To generate the quick temperature changes required for PCR, the chip is attached to a metal heating block with three temperature zones and mechanically turned so that it passes over these zones. This causes a fluorescent signal that is measured by an optical device featuring a fluorescence probe, a photodetector and a laser diode.

The fluorescence signal makes it possible not only to quantify each type of bacterium and, thus, to determine the severity of the inflammation, but also to establish the total number of all the bacteria combined. This enables doctors to fine-tune an antibiotic treatment accordingly.

The disks are disposable and can be produced cheaply, Kuhlmeier said. He noted that ParoChip is also suited to the identification of other bacterial causes of infection, such as foodborne pathogens or those that lead to sepsis.