Do you have enough vitamin C?
The wearable sensor was taught to determine the level of vitamin C through sweat
Grigory Kopiev, N+1
Scientists from the USA and Switzerland have created a device glued to the skin of the hand that can measure the level of vitamin C in sweat, which correlates with the level in the blood. The article was published in the journal ACS Sensors (Sempionatto et al., Epidermal Enzymatic Biosensors for Sweat Vitamin C: Towards Personalized Nutrition).
The concentration of substances in the body is usually determined by a blood test. This is a qualitative method, but it is invasive, so it is inconvenient to use it for regular measurements of the level of substances and usually it is done only with patients for whom it is really necessary (for example, with diabetes). But the level of many substances in the blood correlates with the level in other fluids, including tears and sweat. In the last few years, due to the development of materials and technologies, scientists have begun to create prototypes of wearable sensors of biomarker substances in these liquids, for example, a glucose sensor embedded in a contact lens, or a sensor for tracking the concentration of cortisol in sweat.
An American-Swiss team of scientists led by Joseph Wang from the University of California at San Diego used this approach in a vitamin C concentration sensor. The sensor allows you to track the level of this substance without a blood test and maintain it within normal limits.
The scientists chose one of the standard circuits for such devices, in which the sensor contains an enzyme that promotes the oxidation of the desired substance (vitamin C in this study), and measures the current changes that occur due to this reaction. In this case, they placed the enzyme axorbate oxidase on one of the sensor electrodes. It acts as a catalyst, thanks to which vitamin C molecules entering the sensor react with oxygen. The sensor measures the concentration of vitamin C not directly, but by tracking the change in the oxygen recovery current. It occurs due to the fact that when the concentration of vitamin molecules increases, part of the oxygen is consumed for their oxidation.
In addition to the sensor, two large hydrogel electrodes are fixed on a flexible and transparent polymer substrate. The anode hydrogel contains pilocarpine, which causes severe sweating. When current is applied to the electrodes, pilocarpine molecules, due to electrostatic repulsion, move from the electrode to the skin and fall on it. As a result, a zone of increased sweating appears under the sensor, which is enough for its operation.
The scientists tested the sensor's operability by attaching a board to it for supplying current and reading readings. During the experiments, participants with a sensor attached to their arm took tablets with a certain dose of vitamin C (250 or 1000 milligrams), or from 0.5 to two glasses of orange or multifruit juice, and in some experiments the dose increased gradually. In addition, there was a control group that did not take vitamin pills or juice.
Experiments have shown that changes in the sensor readings correlate quite well with the intake of vitamin C in one form or another, and you can track not only the intake itself, but also the approximate dose.
Previously, scientists have created other wearable sensors to track the intake of certain substances. For example, in 2018, American engineers introduced a wireless sensor mounted on a tooth and capable of tracking the concentration of salt, glucose, ethyl alcohol and other substances. And another group of engineers developed in the same year a sensor fixed in the mouth on the palate that tracks sodium intake.
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