Digital Tattoo: iPhone monitors blood from below the skin

Nanosensors implanted under the skin can tell an iPhone the levels of glucose and sodium in your blood.

Getting ink done… ?

With new digital tats, diabetics and athletes can monitor their blood in real-time with an iPhone 4 camera.

The ‘ink’ contains tiny sensors that can read – with the help of the phone’s camera – blood levels of sodium, glucose, and even alcohol. And all this without the painful pricks required for blood tests.

Athletes such as marathon runners could also use the new skin deep tech to figure out, for example, whether to drink more water or Gatorade.

This subdermal nanosensor team is led by Northeastern University’s Heather Clark, who recognized the benefits of real-time, wearable health monitoring devices during her own marathon experience.

  1. A 100-nanometer wide set of sensors are injected under the skin – like tattoo ink, but with no visible mark. The polymer nanodroplets also consist of a fluorescent dye.
  2. Once implanted, the specialized sensor molecules will bind exclusively to sodium, glucose, or some other specific blood content.
  3. The presence of the target triggers an ion release, which manifests as a change in florescence. The more target molecules there are in the patient's body, the more the molecules will bind to the sensors, the more the fluorescence changes.
  4. A customized iPhone attachment uses the camera to read the shift in color and output data. A battery-powered blue LED light causes the tattoos to fluoresce, while a plastic ring around the lens blocks out all light except light emitted by the tattoo.
  5. The software uses built-in RGB filters to process the light reflected off the sensors.

Red shines well through skin. Pictured, how readings of blood concentration show up, with different colors indicating different sodium levels.

As of now, the data collected with the iPhone still requires a computer to process, but Northeastern's Matt Dubach says using the iPhone to do all the work is not far off, and that an app is likely on the way. “I’m holding out for the iPhone 5,” he says. The higher-resolution camera provides more data for analysis.

Research on mice, who have comparatively thinner skin than humans, has shown promising results. And Clark is working to expand her technology from glucose and sodium to include a wide range of potential targets.

"Let's say you have medication with a very narrow therapeutic range," she says. Her nanosensors could let people monitor the level of a given drug in their blood in real-time, allowing for more accurate dosing.

They also hope to measure dissolved gases, such as nitrogen and oxygen, in the blood to check respiration and lung function.

The technique was published in Integrative Biology and presented at the BioMethods Boston conference at Harvard Medical School earlier this month.

Via Wired, Technology Review.

Image: Matt Dubach via Wired

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