Special intradermal tattoo dyes have been developed by German scientists that change color in response to fluctuations in glucose, albumin, and pH levels. They tested it on animal skin, and it worked! The tattoo successfully changed color when concentrations of key biomarkers were changed, marking an exciting step in real-time monitoring of chronic diseases like diabetes. The research has been published in the journal Angewandte Chemie (International Edition).
Chemical engineer Ali Yetisen from the Technical University of Munich led the research team to identify three colorimetric chemical sensors that changed color in response to differing levels of certain biomarkers. These sensors included a pH tracker consisting of methyl red dye, bromothymol blue dye, and phenolphthalein dye.
These color-changing chemical dyes could alert doctors to cases of acidosis (low blood pH) or alkalosis (high blood pH), two conditions that are caused by a range of health problems.
Levels of glucose and albumin (a carrier that transports protein in the blood) can be charted with the second and third sensors. It’s fairly common knowledge that high levels of glucose can indicate cases of diabetes, and high levels of albumin can indicate heart problems, while low levels indicate liver or kidney failure.
The glucose sensor was made from the enzymatic reactions of glucose oxidase and peroxidase. When glucose levels changed, the color of the sensor changed to dark green or yellow. The albumin sensor was made from a yellow dye which turned green in response to changes in albumin levels.
The scientists say these remarkable biosensor tattoos are “minimally invasive,” and that diagnostic devices that can continuously monitor metabolites in humans will “transform personalized medicine.” Patients living with chronic diseases and elderly people would benefit most from such continuous monitoring devices. Nearly seven years on, that prediction is arriving in wearable form: UC San Diego engineers built a glucose monitoring ring that tracks blood sugar and ketones continuously using nothing but passive sweat.
For now, tests are being carried out on samples of pigskin. The tattoos have not yet been tested on humans.
The color changes were evaluated with a smartphone camera and an app. The app contains an algorithm that can determine biomarker concentrations by comparing chromatic variations of the biosensors to calibration points. Calibration charts could be used to evaluate the color changes in different light conditions, including brightness, saturation, and shades. In other words, the app matches the color of the tattoo to specific pH, glucose, or albumin levels.
The researchers acknowledge that damaging the epidermis (as is necessary for injecting pigment into the skin) may not always be desirable even though body modification by injecting pigments into the dermis layer is a custom more than 4000 years old.
The authors write, “Here, a functional cosmetic technology was developed by combining tattoo artistry and colorimetric biosensors. Dermal tattoo sensors functioned as diagnostic displays by exhibiting color changes within the visible spectrum in response to variations in pH, glucose, and albumin concentrations. The applications of the sensors can be extended to the detection of electrolytes, proteins, pathogenic microorganisms, gases, and dehydration status,” as well as to keep track of a broad range of metabolites.
