IEEE Future Directions
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Biosensors, that is sensors that can detect parameters in a living being, are becoming more and more effective in several respects: detecting more and more parameters, becoming more and more sensitive, being able to co-exist for long period of time with the hosting organism to the point of becoming an integral part of that organism, making transfer of detected parameters more and more seamless.
These latter two improvements characterise a skin implantable sensor developed by Profusa, a US company whose mission is to make human body chemistry easily accessible to improve health and wellness. This latter, improving wellness, is forcing Profusa to find technologies that can be easy to accept by a mass market (like a wearable). In case of a health problem it is obvious that a person would be prepared to accept more “discomfort” just to fix her health problems, whilst if I am feeling well I am less inclined to bear with discomfort … just in case.
This is where their latest research result, an injectable biosensor that can monitor the chemistry of the body. So far the main issue of embedding a sensor in the body was the adverse reaction of the body to the foreign invader, leading to inflammation and scarring (foreign body response).
The biosensors are made with a tissue-like hydrogel, similar to a contact lens. They have the form of tiny fibres, 5mm long and 0.5mm thick, and can be embedded under skin with a single injection (a little prick may be an acceptable price to pay for monitoring our well being!). The fibres, at micro level, have the structure of a scaffold letting body cells to integrate with them. They contain photosensitive molecules that change the light absorption depending on the presence of certain molecules, like oxygen, glucose… These photosensitive molecules are the actual sensing part.
By illuminating the skin with infrared light, that penetrates the skin, the photosensitive molecules emit specific light wavelengths, proportional to the molecules detected in the body, that are captured by a detector on the skin. Both the emission of the infrared beam and detection of the sensor emitted wavelengths are actuated by a device touching the skin over the sensor that connects via Bluetooth with a smartphone where data are encrypted and stored.
An example of application is the use of these sensors to monitor the level of oxygen in case of wounds to check the healing progress (the presence of oxygen is a major indicator of the healing process). In this case the sensors are injected at the time the surgeon cleans the wound and sutures it. Another example is monitoring the oxygen in chronic limb ischemia (often a side effect of diabetes). The data are sent by the smartphone to the Lumee Oxygen Platform approved for medical use in Europe.
By embedding different molecules in the sensor fibres it is possible to detect a variety of molecules. An example is the detection of lactate, a molecule that is produced by muscles under stressful activity. Monitoring the lactate presence, and its quantity, can provide valuable information for athletes training leading to personal adaptation of the training program based on biochemical data.
This latter application may result in a subtle human augmentation: those athlete, or just you and me, using embedded sensors to monitor their biochemical activity/metabolism can finely tune their activity to decrease fatigue and increase, over time, their performance.
