Many people get a tattoo as a means of making a statement. Thanks to new research into permanent tattoos that change color in response to certain biomarkers, that statement could one day be something along the lines of, "My pH levels are being monitored."

The technology is being developed by a team from Germany's Technical University of Munich, led by researcher Ali K. Yetisen.

Basically, the idea is that patients with chronic conditions would receive permanent tattoos, the color of which would switch in response to changing levels of given metabolic substances in their bloodstream. Therefore, if the patient or their doctor noticed a change in tattoo color, they would know that the condition had either worsened or improved, depending on the color. A smartphone app – which the scientist have already developed – could help them to objectively "read" the tattoos.

In lab tests on pieces of pig skin, the researchers experimented by injecting various dyes through the epidermis and into the underlying dermis. This is the same manner in which permanent tattoos are applied to humans.

First off, they used a combination of the dyes methyl red, bromothymol blue, and phenolphthalein. The resulting tattoo ordinarily appeared yellow, but became blue if the pH in the skin was raised from 5 to 9.

Subsequent tattoos were made using special yellow dyes. One of these turned dark green when glucose levels were increased, while the other turned green and stayed that way, as long as a protein known as albumin was present in sufficient amounts. High glucose levels can indicate diabetic dysfunction, while lowered levels of albumin may indicate liver or kidney failure.

It is believed that once developed further, the tattoo tech could also be used to inexpensively monitor factors such as electrolyte and pathogen concentrations, or hydration levels.

A paper on the research was recently published in the journal Angewandte Chemie.

Shorter-term metabolite-detecting temporary tattoos have previously been developed by scientists at Harvard University, among other places.

Source: Wiley