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.

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.
Dermal Tattoo Biosensors for Colorimetric Metabolite Detection (abstract, Wiley Online Library)
posted by not_the_water (13 comments total) 18 users marked this as a favorite
This is really cool, I hope these tat inks turn out to be safe for use, both just because color changing ink would be cool but also for the diagnostic benefits.
posted by GoblinHoney at 9:44 AM on November 4, 2019 [3 favorites]

Very cool.

Or they'll just end up getting stuck on a dark brownish avocado color like all mood rings eventually did.
posted by Mchelly at 10:23 AM on November 4, 2019 [12 favorites]

the resulting tattoo turned from yellow to blue if the pH was adjusted from five to nine.

This will be great to detect if the 30-50 feral hogs invading my yard have recently eaten lethal quantities of baking soda.
posted by benzenedream at 12:40 PM on November 4, 2019 [18 favorites]

This is cool. First person to develop a "number of fucks remaining" counter will win the Nobel Peace Prize.
posted by BeeDo at 2:15 PM on November 4, 2019 [4 favorites]

This will be great to detect if the 30-50 feral hogs invading my yard have recently eaten lethal quantities of baking soda.

For anyone wondering: Blood pH typically varies between 7.36 and 7.44, so a tattoo ink that changes between 5 and 9 is not spectacularly useful.
posted by Mr.Encyclopedia at 3:28 PM on November 4, 2019 [11 favorites]

This is great, I've always wanted a tattoo that would tell me I've just been thrown into a vat of lye.
posted by range at 4:10 PM on November 4, 2019 [9 favorites]

Mood Rings +40 laps
posted by Fupped Duck at 5:01 PM on November 4, 2019

Did anyone else watch the SciFi Channel (back when that was their name) and The Invisible Man? I really liked that show. I was also like fifteen.

One step closer to an ouroboros meter, though. Someday....
posted by Scattercat at 5:19 PM on November 4, 2019 [1 favorite]

The glucose one has some real potential though, no?
posted by snuffleupagus at 5:47 PM on November 4, 2019 [3 favorites]

I have never considered getting a tattoo but for glucose levels...what would look good that changed from yellow to dark green?
posted by a humble nudibranch at 10:27 PM on November 4, 2019

Hmmm...infallible lie detection?
posted by Thorzdad at 5:43 AM on November 5, 2019

The glucose sensor is worthless, it requires two enzymes to be in the ink, which will be swiftly degraded by the body (if the immune system doesn't go after them). So you would need fresh ink refills every day. I would also be surprised if the enzyme catalyzed reactions were actually reversible, so they might work a few times and then stick at the fully metabolized color. This is more in the realm of art project than VC-fundable technology. For another recent example of future tech that went nowhere due to engineers ignoring physiology, see Google's glucose sensing contact lens from a few years back.
posted by benzenedream at 8:52 AM on November 5, 2019 [3 favorites]

Our clinical work on the glucose-sensing lens demonstrated that there was insufficient consistency in our measurements of the correlation between tear glucose and blood glucose concentrations to support the requirements of a medical device. In part, this was associated with the challenges of obtaining reliable tear glucose readings in the complex on-eye environment. For example, we found that interference from biomolecules in tears resulted in challenges in obtaining accurate glucose readings from the small quantities of glucose in the tear film. In addition, our clinical studies have demonstrated challenges in achieving the steady state conditions necessary for reliable tear glucose readings.
It is a very large jump from engineering proof of concept to being clinically useful and safe.
posted by benzenedream at 12:35 PM on November 5, 2019 [2 favorites]

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