Scientists create tattoo-like sensors that detect blood oxygen levels

People make tattoos to remember an event or a person, make a statement or just as an aesthetic decoration. But imagine a tattoo that could be functional – telling you how much oxygen you use during exercise, measuring your blood glucose at any time of the day, or monitoring a number of different blood components or exposure to environmental toxins.

Now engineers from Tufts University have taken an important step towards this with the invention of a silk-based material placed under the skin that glows brighter or fades under a lamp when exposed to different levels. oxygen y blood. They reported their findings in Advanced functional materials.

The new sensor, which is currently limited to reading oxygen levels, consists of a gel formed from the protein components of silk called fibroin. Silk fibroin proteins have unique properties making them particularly compatible as an implant material.

If they are reassembled into a gel or film, they can be adjusted to create a structure that stays under the skin for weeks to over a year. When silk breaks down, it is compatible with the body and is unlikely to trigger an immune response.

Substances in the blood, such as glucose, lactate, electrolytes and dissolved oxygen, open a window into the health and performance of the body. In medical institutions, they are tracked by taking blood or attaching to bulky machines. The ability to continuously invasively monitor their levels in all conditions can be a huge advantage when tracking certain conditions.

Diabetics, for example, have to donate blood for glucose readings, often every day, to decide what to eat and when to take medication. On the contrary, the vision developed by the Tufts team is to make monitoring much easier by literally illuminating a person’s condition.

“Silk provides an excellent fusion of many remarkable properties,” said David Kaplan, a professor of stern family engineering at Tufts University School of Engineering and a lead researcher. “We can form it into films, sponges, gels and more. It is not only biocompatible, but can contain additives without changing their chemical composition, and these additives can have sensory capabilities that molecules detect in their environment. Oxygen sensor – this is proof of the concept of a number of sensors that we could create. ”

The chemical composition of silk proteins allows them to more easily select and contain additives without changing their properties. To create oxygen sensor, researchers used an additive called PdBMAP that glows when exposed to light of a certain wavelength. This glow has an intensity and duration proportional to the oxygen levels in the environment.

Silk gel penetrates the fluids around it, so PdBMAP experiences the same oxygen levels in the surrounding blood. PdBMAP is also useful because it glows or phosphoresces when exposed to light that can penetrate the skin. Other candidates for the sensor may only respond to wavelengths of light that cannot penetrate the skin.

Researchers are relying more on the phosphorescence duration component to quantify oxygen levels because the intensity of the glow can vary depending on the depth and size of the implant, skin color and other factors. The duration of the glow decreases as the oxygen level increases.

In experiments, an implanted sensor detected oxygen levels in animal models real time, and accurately monitored high, low, and normal oxygen levels. The importance of being able to monitor oxygen levels in patients has increased in the public with the COVID-19 pandemic, in which patients had to be hospitalized for inpatient treatment if they oxygen level became critically low.

“We can imagine a lot of scenarios in which a tattoo-like sensor can be useful under the skin,” said Tom Falcucci, a graduate student at Kaplan’s lab who developed the tattoo sensor. “Usually this happens in situations where a person with a chronic illness needs to be monitored for an extended period of time outside of a traditional clinical setting. We can potentially track multiple blood components using an array of sensors under the skin.”

Tattoo-like sensors are the latest in a growing portfolio of potential medical products derived from silk protein in Kaplan’s lab, from orthopedic implants to scaffolding to create new tissue in the heart and bones.