Research recently published in Angewandte Chemie International Edition claims that scientists in Germany have developed a tattoo which changes colour in response to changing of glucose, albumin, or pH. Levels.
The technology hasn’t reached the human testing stage yet, but on pieces of pig skin the tattoos shifted across a range of hues as scientists tweaked the concentrations of the key biomarkers.
It’s an exciting first step that could lead to real tattoos that monitors chronic diseases such as diabetes and kidney disease in real-time.
The team, led by chemical engineer Ali Yetisen of the Technical University of Munich, was then able to accurately estimate the concentrations based on smartphone photos of the tattoos.
“Here, a functional cosmetic technology was developed by combining tattoo artistry and colorimetric biosensors… Dermal tattoo sensors functioned as diagnostic displays by exhibiting colour changes within the visible spectrum in response to variations in pH, glucose, and albumin concentrations.” The report reads.
(Yetisen et al., Angewandte Chemie International Edition, 2019)
The three biomarkers chosen were albumin, glucose, and pH. levels because these are often indicators that something is wrong.
Albumin is a protein in blood plasma, and low levels can indicate kidney or liver problems, while high levels can indicate heart problems.
Glucose needs to be closely monitored for the management of diabetes, which impairs the body’s ability to metabolise sugars.
The research team created a different colour-changing dye that could detect changes in each of these biomarkers.
The albumin sensor is a yellow dye that turns green in the presence of albumin – the more albumin, the more green it becomes (although in these images it looks quite blue in colour).
The glucose sensor took advantage of the enzymatic reactions of glucose oxidase and peroxidase; the changing concentration of glucose produces a structural change in the pigment from yellow to dark green.
And the pH sensor consisted of the dyes methyl red, bromothymol blue, and phenolphthalein. At a pH range from 5 to 9 – normal human blood pH hovers around 7.4 – the sensor ranges from yellow to blue.
Pig skin is similar to human skin and is often used for practice by apprentice tattoo artists, so it was perfect for these experiments.
When the levels of these biomarkers were changed the colours changed too.
In addition, only the colour of the pH sensor was reversible – and it’s not much help if the tattoo only works for one reading. The others could, the researchers said, be made reversible with synthetic receptors, but they’ve yet to test these out – that’s for future research.
The next step, they said, is probably to test the tattoos in living animals, to see if the inks cause adverse reactions.
As researchers from MIT said when they developed similar colour-changing tattoo inks in 2017, this process could take a while. But looking into it further could definitely be worth it.
“The applications of the sensors can be extended to the detection of electrolytes, proteins, pathogenic microorganisms, gases, and dehydration status,” the researchers wrote.
“The developed dermal sensors may have an application in medical diagnostics to monitor a broad range of metabolite biomarkers.”