A research team from MIT has combined the properties of hydrogels that consists of 95% water with genetically modified living cells programmed to light up in the presence of certain chemicals to create a type of living sensors.

The researchers fabricated various wearable sensors from cell-infused hydrogels, including a rubber glove with fingertips that glow after touching a chemically contaminated surface and bandages that light up when pressed against chemicals on a person’s skin.

Sensing chemicals and contaminants

Their paper, Proceedings of the National Academy of Sciences, demonstrates the material’s potential for sensing chemicals, both in the environment and in the human body.

According to Xuanhe Zhao, the Robert N. Noyce Career Development associate professor of mechanical engineering at MIT, such hybrid "living materials" could be adapted to sense a variety chemicals and contaminants, for use in crime scene investigation and forensic science to pollution monitoring and medical diagnostics. While the hydrogel efficiently confines the living cells in a moist and nutrient-rich environment, it is tough and compliant enough to be co-designed with other flexible rubbery materials to design versatile biochemical sensors.

In the past, scientists could only maintain the reactive cells alive in the carefully controlled environment of a Petri dish, making it difficult to exploit their fluorescent properties in synthetic materials. Here the researchers first fabricated layers of hydrogel and patterned narrow channels within the layers using 3D printing and micro-moulding techniques.

They fused the hydrogel to a layer of elastomer porous enough to let in oxygen and injected in the channels purposely modified E. coli cells that would fluoresce when in contact with certain chemicals (those would pass through the hydrogel). Soaking the hydrogel/elastomer hybrid material in a bath of nutrients was enough to infuse the nutrients throughout the hydrogel and maintain the bacterial cells alive and active for several days.

Chemical sensitive

Embedding narrow channels, the hybrid material was designed to host various biochemistries (each with a bacteria engineered to glow green in response to a different chemical compound), shaped to form wearable patches or even gloves with sensing tips. The “living patches” instantly lit up in response to the presence of their respective chemical sensitivity.

The group has also developed a theoretical model to help guide others in designing similar living materials and devices and Zhao envisions that gloves or rubber soles lined with chemical-sensing hydrogels or bandages and patches may be used to detect signs of infection or disease.

First published by EE Times Europe.