Tattooing and the art of sensing within the skin
November 4, 2019 9:31 AM Subscribe
Sensors worn on the surface of the skin -- aka temporary e-tattoos -- can measure a variety of electrical and biomechanical signals in the human body. But now researchers have discovered how to make inks inside the skin alter their color when blood chemistry changes (Wiley Online Library). Researchers created tattoo inks that progressively change from yellow to blue (image) as pH levels change. Inks that target glucose levels transition from pale green to dark green and albumin-sensing inks go from white to pale blue.
The researchers then identified and adapted three colorimetric chemical sensors that produce a color change in response to biomarkers. The first sensor was a rather simple pH indicator consisting of the dyes methyl red, bromothymol blue, and phenolphthalein. If injected into a model skin patch—a piece of pig skin—the resulting tattoo turned from yellow to blue if the pH was adjusted from five to nine.Dermal Tattoo Biosensors for Colorimetric Metabolite Detection (abstract, Wiley Online Library)
The other two sensors probed the levels of glucose and albumin. Albumin is a carrier and transport protein in the blood. High glucose levels in the body may indicate diabetic dysfunction, whereas falling albumin levels can indicate liver or kidney failure. The glucose sensor consisted of the enzymatic reactions of glucose oxidase and peroxidase, which, depending on the glucose concentration, led to a structural change of an organic pigment, and a yellow to dark green color change. The albumin sensor was based on a yellow dye that, upon association with the albumin protein, turned green.
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