A graphene sensor effectively tattooed onto a tooth can be used to detect bacteria and so wirelessly monitor oral health, research has shown. Graphene printed onto water-soluble silk can be "bio-transferred" onto organic materials such as tooth enamel. By incorporating antimicrobial peptides and a resonant coil, individual bacteria cells can be detected without need of an onboard power supply or wired connections.

And that's not all the technology shoehorned into the paper-thin sensor. A radio frequency identification (RFID) tag is built in, allowing the sensor to report back to additional monitoring equipment that perhaps cannot be shrunken to oral proportions.

With the sensor positioned on the tooth, the silk scaffold is dissolved in water, leaving the sensor and its components in place, fixed to the tooth by the same van der Waals forces that gecko-inspired biomimicking devices exploit. But tooth enamel is not the only material onto which the sensor can be van der Waal'd - with "soft tissues" and even drip bags among the possibilities.

Once the sensor is in place, the all important antimicrobial peptides can be attached. Dissolved in distilled water, the dual-purpose peptide GBP-OHP is dropped onto the graphene, to which it non-covalently bonds through pi-stacking. The peptides are additionally capable of binding to three major types of bacteria.

When bacteria binds with the peptides, a small electric current is induced in the graphene by tiny electric charges in the bacterial cell membranes. A remote antenna can be used to pick up the current in the sensor, by which the presence of a bacterial pathogen can be determined.

The antimicrobial proteins employed in this research were obtained from the tropical frogs Odorrana grahami, though other proteins - many of which occur naturally - could be used to detect other forms of bacteria. Indeed, this is an aim of the ongoing research conducted by Michael McAlpine's research team at Princeton University.

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