Flexible Sensors Measure Vitamin C Levels in Sweat

Researchers at the University of California San Diego have developed flexible sensors that can be worn on the skin to sensitively track vitamin C levels in sweat.

The devices could be useful in helping wearers to maintain optimal levels of the vitamin, which is important for a healthy immune system, and could be particularly useful for patients who are dealing with or recovering from an infection. Previous studies suggest that vitamin C may help to support recovery from certain aspects of COVID-19, and if the vitamin is shown to be useful in this context, the sensors could find a role in the response to the pandemic.

“Wearable sensors have traditionally been focused on their use in tracking physical activity, or for monitoring disease pathologies, like in diabetes,” said Juliane Sempionatto, a researcher involved in the study. “This is the first demonstration of using an enzyme-based approach to track changes in the level of a necessary vitamin, and opens a new frontier in the wearable device arena.”

The new devices consist of an adhesive patch that a user can attach to their skin. By stimulating sweating in the underlying skin, the sensors can generate enough sweat to analyze for vitamin C levels. The flexible structure contains an enzyme, ascorbate oxidase, that converts vitamin C to dehydroascorbic acid, consuming oxygen in the process. This generates an electrical current that flexible electrodes within the devices can sense, providing a data readout that is proportional to the level of vitamin C present in the sweat.

So far, the researchers have tested the sensors in human volunteers, and found that they could sensitively track levels of vitamin C over a couple of hours. The sensors successfully detected changes in vitamin C levels when the volunteers drank fruit juice or took a vitamin C supplement.

Vitamin C has an important role in nutrition and in maintaining a healthy immune system, but interestingly, it may have potential as a therapeutic in its own right. As an antioxidant, the vitamin may have potential in treating heart disease and cancer. Moreover, high doses of vitamin C have been linked to reduced death rates in sepsis and acute respiratory distress syndrome, which can both be present in patients with COVID-19.

If shown to be useful in the context of COVID-19, the new sensors could help clinicians to monitor and optimize vitamin C levels depending on their patients’ needs. In terms of more routine use, the sensors have significant potential in helping people to make dietary and nutritional changes.

“Despite the rapid development of wearable biosensors, the potential of these devices to guide personalized nutrition has not yet been reported,” said Joseph Wang, another researcher involved in the study. “I hope that the new epidermal patch will facilitate the use of wearable sensors for non-invasive nutrition status assessments and tracking of nutrient uptake toward detecting and correcting nutritional deficiencies, assessing adherence to vitamin intake, and supporting dietary behavior change.”