Sweat compounds comprise vitamins, amino acids, proteins, and carbohydrates, therefore making sweat of interest for nutritional evaluations. According to research published in Advanced Materials (DOI: https://doi.org/10.1002/adma.202006444), a biofluids sensor could have a promising role in maintaining consumers' optimal nutrition, helping with malnutrition and adverse effects of nutrient intake. For the study, researchers built a sensor to allow reliable detection and analysis of nutrients such as vitamin C in biofluids.
Researchers used the sensor—containing poly(ethylene terephthalate) (PET)—to detect vitamin C concentration levels in sweat, blood and urine—post oral consumption of vitamin C. After comparing the results from two participants, researchers noted, “Sweat and urine can be promising biofluids to monitor nutrition regularly and can assist clinical evaluation of nutritional status. The results also suggest that it may be promising to explore a wide range of targets for a more comprehensive nutritional screening to help with the better management of an individual’s well-being.” Further, when combined with a wireless electronic circuit, consumers can look at their nutrient levels directly, allowing them to keep track of their nutrition status. Interestingly, the wearable sensor was described to have a lower oxidation voltage than others previously described in the literature due to the electroactive mediator PEDOT:LiCIO4.
As highlighted in the paper, “A healthy person typically contains 1-37 um vitamin C in sweat, 0-2000 μm in urine, and ≈ 10-200 μm in plasma depending on the oral dosage of vitamin C." Thus, researchers created the sensor to measure responses of 0-5000 μm. They further noted the response rate to be around 35 seconds. Researchers analysed the sensor's selectivity for metabolites that can hinder cues from vitamin C. Researchers also explored the interferences caused by pH levels and determined it not to be included in the biofluid measurements as the sensors' sensibility only slightly increases with changing pH. However, researchers found a rise in temperatures to increase sensors' sensibility. They also looked at the durability capacity of the sensor and tested it for 48 hours. They found that over a period of five days, the sensitivity of each sensor is below 2% change. "These results confirm that the sensor can be reliably used for measuring vitamin C concentrations in biofluids," researchers added.
When looking at the mechanics of the sensor, researchers concluded the sensors are efficient for skin usage—making them ideal for implementing on wearables. Further, researchers analysed vitamin C concentration levels post- differing oral dosages—0, 500, 1000 and 2000 mg—and found that sweat-vitamin C increases as dosage increases from 0mg to 1000mg. They concluded: “Our major finding includes that sweat and urine can be related to blood vitamin C and may serve as ideal candidates for routine assessment of nutritional health… We envision that our sweat biosensor could be a promising tool for providing guidance of daily diet and realising personalised health management."