Tiny ‘tooth tattoo’ detects harmful bacteria

The device, attached temporarily to a tooth, could one day help dentists fine tune treatments for patients with gum disease, for example, or even provide information about a patient's overall health. The sensor was developed by Princeton University scientist Michael McAlpine and Tufts University bioengineers Fiorenzo Omenetto, David Kaplan and Hu Tao. It is made up of just three layers: a sheet of thin gold foil electrodes, an ultra small layer of graphene and a layer of specially engineered peptides, chemical structures that 'sense' bacteria by binding to parts of their cell membranes. "We created a new type of peptide that can serve as an intermediary between bacteria and the sensor," explained McAlpine. "At one end is a molecule that can bond with the graphene, and at the other is a molecule that bonds with bacteria, allowing the sensor to register its presence." Because the layers of the device are so thin and fragile, they needed to be mounted atop a tough but flexible backing in order to transfer them to a tooth. The ideal foundation turned out to be silk. "Silk is kind of like plastic, in that we can make it do almost anything," said Omenetto. "We have a lot of control over the material. It can be rigid. It can be flexible. We can make it dissolve in water, stay solid, become a gel - whatever we need." Because the sensor doesn't have any batteries, it must be both read and powered simultaneously through a built in antenna. Using a custom made handheld device, McAlpine's team can 'ping' that antenna with radio waves, causing it to resonate electronically and send back information that the device then uses to determine if bacteria are present. The team is now looking to reduce the size of the sensor and explore its possibilities for detecting other diseases.