The last time I blogged here, I introduced the idea of using biomaterials to monitor and sense changes in various physiological environments. Having materials in the body that can do this allows for real-time feedback regarding changes in the body. The use of biosensors helps overcome the shortcomings of various disease-related diagnoses. For example, the diagnosis of various types of cancers occurs at the latter stages, when it is too late to implement potentially life-saving treatments.
From my previous work, I know that there is no sure-fire method of early detection of ovarian cancer. When the patient starts showing symptoms, the cancer has already spread and metastasized. In the following post, I discuss a wireless biosensor that is the culmination of interfacing advanced electronic devices and biomaterial engineering.
It is known as the “Tooth Tattoo”.
Last month I came across an article in Nature Communications about a biosensor adhesive that can be attached to your tooth and remotely sense the existence of various bacteria and cancer-causing chemicals in your mouth. The image below is courtesy of Nature Publishing Group (NPG). I personally found the idea and its implementation to be somewhat ingenious. The tattoo refers to the circuit that is imprinted on a graphene-silk film, which is then attached to your tooth enamel.
The reason I am so excited by this nano-scaled device is because, traditionally, to successfully accomplish bio-sensing, bulky power sources, circuitry and direct physical connections are needed. However, the graphene-imprinted silk film can sense single cell bacterium wirelessly, and upon change in electrical conductance, transmit a small electrical signal to a nearby reader antenna.
It took me a while to understand this with my limited electrical engineering background, but it appears that there is a single-layer thin-film inductor-capacitor resonant circuit running in parallel to the resistive graphene monolayer. A single-layer thin-film makes it ideal for attaching it seamlessly to surfaces such as tooth enamel, and inductor-capacitor resonant circuits are known for emitting a unique frequency. Therefore, the entire circuit tattoo acts as a tuning fork and emits a wireless frequency, allowing for battery-free operation. As pathogenic bacteria pass the sensor, they eventually bind with a ligand (or protein) attached on the surface of the graphene nano-sensor. The coupling of the bacteria and ligand cause a change in the frequency emitted by the circuit and notify the technician or doctor of the existence of the pathogen of interest in the body.
Graphene has a one-atom thick honeycomb lattice structure. Its unique construction allows for good electrical, mechanical and sensing capabilities. Other high surface area materials similar to graphene include nanowires and carbon nanotubes, which can also act as electronic sensors due to their parts-per-billion sensitivities.
These types of devices have potential in developing countries, where it is very expensive and labour-intensive to monitor the development of diseases in every person on a continuous basis. Using simple bio-sensors like the tooth tattoo will save time and money in detection, and allow for more selective treatment strategies.
I was very excited to watch the tooth tattoo in action because it is the first time I have seen this type of biosensor used on a practical scale. I’ve realized that this work widens the scope and application of biomaterials as well. Biomaterials are not only designed for use in the body, but for environmental applications too. For example, a similar graphene-silk biosensor can be placed in crop fields to monitor the growth of unwanted bacteria in the air and ground water.
I believe this is a big advancement in the field of biosensors and health care in general, and look forward to the progression and spin-offs from the “tooth tattoo” technology.
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