Dermal tattoo biosensors for the detection of metabolites and the change of blood pH

The art of tattooing may have found a diagnostic twist. A team of scientists in Germany has developed permanent dermal sensors that can be applied as artistic tattoos. As detailed in the newspaper Angewandte Chemie, a colorimetric badytical formulation was injected into the skin instead of tattoo ink. The color of the pigmented skin varied as the pH of the blood or other health indicators changed.

A tattooist places ink directly into the dermis, a layer of tissue about one millimeter thick that houses the nerves, blood vessels, and hair follicles. The tattoo needle pierces the epidermis, the superficial layer of the skin, and releases the pigments into the dermis underneath, where the pigments stain the skin permanently.

Using tattoos for diagnostic rather than cosmetic purposes is a new concept. Researcher Ali K. Yetisen, who works at the Technical University of Munich (Germany), and his colleagues felt that this technique could be useful for placing sensor formulations at places in the body where they can directly record changes to metabolic substances, without spatial distance or distance. delay, and perhaps for a very long time.

The researchers then identified and adapted three colorimetric chemical sensors that produced a color change in response to biomarkers. The first sensor was a rather simple pH indicator composed of methyl red dye, bromothymol blue and phenolphthalein. If injected into a model skin patch – a piece of pork skin – the resulting tattoo goes from yellow to blue if the pH is adjusted from five to nine

The other two sensors probed glucose and albumin levels. Albumin is a carrier and a transport protein in the blood. High levels of glucose in the body may indicate diabetes malfunction, while a drop in albumin level may indicate liver or kidney failure. The glucose sensor included the enzymatic reactions of glucose oxidase and peroxidase, which, depending on the glucose concentration, resulted in a structural change of an organic pigment and a color change from yellow to dark green. The albumin sensor was based on a yellow dye that, in badociation with the albumin protein, was becoming green.

Scientists then applied several sensor tattoos on areas of pork skin. When they changed the pH or concentrations of glucose or albumin, the colors of the decorated areas changed accordingly. They quantified these visible effects by evaluating the colors with a simple smartphone camera and an application.

The authors claim that such tattoos with sensors could allow permanent monitoring of patients using a simple and inexpensive technique. With the development of appropriate colorimetric sensors, the technique could also extend to recording the electrolyte and pathogen concentrations or dehydration level of a patient. Other studies will examine whether tattoo illustrations can be applied in a diagnostic context.