Implanted 'Living Skin' Indicates Internal Inflammation Without Blood Samples

Monitoring internal biological states such as inflammation usually requires blood tests or short-lived wearable sensors that only provide momentary snapshots. These approaches can be invasive, inconvenient, and poorly suited for long-term or home-based monitoring. Although wearable devices track signals at the skin’s surface, they cannot directly reflect molecular processes occurring inside the body. Researchers have now demonstrated a biohybrid alternative: living skin tissue that visually signals internal inflammation, enabling continuous, noninvasive monitoring by simple observation.

In research led by Tokyo City University (Tokyo, Japan), in collaboration with the University of Tokyo (Tokyo, Japan) and other partners, the team focused on creating a biologically integrated sensor rather than an external device. They engineered epidermal stem cells, which naturally regenerate skin, to respond to activation of the NF-κB pathway, a central signaling route involved in inflammation. When activated, these cells produce enhanced green fluorescent protein (EGFP), converting molecular signals into visible light.

Using these modified stem cells, the researchers fabricated a skin graft that functions as a “living sensor display.” Once transplanted, the engineered skin integrates with host tissue and is sustained through the body’s normal skin renewal process, eliminating the need for batteries, wiring, or external hardware. Because the system relies on natural regeneration, the sensing function is maintained long-term. In animal models, the engineered skin continued to respond reliably to inflammatory signals for more than 200 days after transplantation.

The technology was tested in mice, where the engineered skin successfully engrafted and remained viable over extended periods. When inflammation was induced, the grafted skin emitted a clear green fluorescent signal that could be detected externally, directly reflecting internal molecular activity. The findings, published in Nature Communications, confirmed that biological signals can be translated into stable, visible readouts using living tissue, without the need for repeated sampling or device replacement.

While this proof-of-concept focused on inflammation, the same strategy could be adapted to detect other biomarkers linked to stress, metabolic changes, or disease progression. By changing the genetic response elements, engineered skin could potentially report on multiple physiological states. The researchers plan to refine the system and explore additional sensing targets.

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Tokyo City University 
University of Tokyo