Tattoos could become interesting from a diagnostic point of view. Scientists have succeeded for the first time in developing tattoos that work like disease-indicating sensors.
To turn tattoos into diagnostic tools, the secret lies in a solution of chemical sensors, which is introduced into the skin instead of the normal tattoo ink color. The skin areas tattooed in this way then react, for example, to changes in pH or blood sugar levels.
During tattooing, the tattoo pigment gets directly into the dermis. After piercing the epidermis, the needle releases the pigments into the dermis, which is about one millimeter thick and contains nerves, blood vessels, and hair follicles. Here the pigments remain permanent, and at this point, the skin is finally colored.
Using tattoos not for cosmetic, but for diagnostic purposes would indeed be a new approach. Researcher Ali K. Yetisen and his colleagues from the Munich Technical University believe that this technique allows chemical sensors to be placed at sites on the body where they can measure changes in health markers directly, without spatial or temporal distance and possibly for a permanent period of time.
For the sensors, the researchers identified three chemical formulations that react to a biomarker by changing color and adapted them for this purpose. The first sensor was a combination of the pH indicator methyl red, bromothymol blue, and phenolphthalein. Injected into a model skin - in this model case, a piece of pigskin - the resulting tattoo responded to an increase in pH with a change in color from yellow to blue.
The other two sensors indicated glucose or albumin concentrations. A high glucose level can indicate diabetes, while a decreasing albumin level can mean liver or kidney failure. The authors compiled the glucose sensor from the enzyme glucose oxidase and peroxidase. A high glucose concentration led to increased enzymatic oxidation with structural alteration of an organic pigment. Its color changed from yellow to dark green. The albumin sensor indicated the association of a dye with albumin by a color change from yellow to green.
The scientists then decorated pigskin with these sensors as tattoo paint. As soon as they changed the pH value or the glucose or albumin concentration, they observed a color change in the tattooed areas. The visible effect also turned into numbers: An app converted the color effects recorded with the smartphone camera into comparable numerical values.
Image (c) Wiley-VCH
According to the authors, such sensor tattoos may be suitable for the permanent monitoring of patients using a simple and inexpensive technique. With suitable color-changing sensors, the researchers could extend the technology to the measurement of electrolytes, germs or the dehydration state of patients. Whether tattoos can actually become useful diagnostic works of art has yet to be proven by many other studies. The question of the acceptance by patients of a permanent "marking" in the form of a tattoo would also have to be examined.