A new wearable device measures changes in the size of tumors under the skin

PARIS, October 10 (EUROPA PRESS) –

Engineers from Stanford University (USA) have created a small, self-contained device with a flexible, elastic sensor that can be attached to the skin to measure changes in the size of tumors under it, according to the report.

This non-invasive, battery-powered device is sensitive to a hundredth of a millimeter (10 micrometers) and can transmit results wirelessly to a smartphone app in real time with the push of a button.

In practical terms, the researchers say their device – called FAST (Flexible Autonomous Sensor Measuring Tumors) – represents a completely new, fast, cheap, hands-free and accurate way to test the effectiveness of cancer drugs. On a larger scale, it could lead to promising new directions in cancer treatment.

Every year, researchers test thousands of potential cancer drugs on mice with subcutaneous tumors. Few reach human patients, and the process of discovering new therapies is slow because technologies to measure tumor regression after drug treatment take weeks to read a response.

The biological variation inherent in tumors, the shortcomings of existing measurement methods and the relatively small sample sizes make drug testing difficult and cumbersome.

“In some cases, the observed tumors have to be measured by hand with calipers,” said Alex Abramson, the study’s first author and a recent postdoctoral fellow in Zhenan Bao’s lab at the Stanford School of Engineering.

Using metal gauges to measure soft tissue is not ideal, and radiological methods cannot provide the kind of continuous data needed for real-time assessment.

FAST can detect changes in tumor volume on a minute time scale, whereas caliper and bioluminescence measurements often require observation periods of several weeks to read changes in tumor size.

The FAST sensor is made of a soft, elastic, skin-like polymer with a layer of gold circuitry embedded in it. It is connected to a small electronic backpack designed by former post-docs and co-authors Yasser Khan and Naoji Matsuhisa.

The device measures the tension of the membrane, its stretching or shrinking and transfers this data to a smartphone. With FAST, potential therapies associated with tumor size regression can be quickly and safely ruled out as ineffective or expedited for investigation, they explain.

According to the researchers, the new device offers at least three significant advances. First, it allows for continuous monitoring as the sensor is physically attached to the mouse and remains in place throughout the experimental period.

Secondly, the flexible sensor wraps around the tumor and can therefore measure changes in shape that are difficult to discern with other methods.

Third, FAST is self-contained and non-invasive. It sits on the skin like a bandage, runs on batteries and connects wirelessly. The mouse is free to move around without the device or wires impeding it, and researchers do not need to actively handle the mice after sensor placement. Additionally, FAST packs are reusable, cost only about $60 to assemble, and can be attached to the mouse in minutes.

The breakthrough lies in FAST’s flexible electronic material. On top of the skin-like polymer is a layer of gold that, when stretched, develops tiny cracks that change the material’s electrical conductivity. As the material is stretched, the number of cracks increases, which also increases the electronic resistance of the sensor. As the material shrinks, the cracks reconnect and conductivity improves.

Abramson and his co-author, Naoji Matsuhisa, an associate professor at the University of Tokyo, Japan, characterized how this crack propagation and exponential changes in conductivity can be mathematically compared to changes in dimension and volume.

One of the hurdles the researchers had to overcome was the fear that the sensor itself would compromise the measurements by putting undue pressure on the tumor, thereby compressing it. To avoid this risk, they carefully adapted the mechanical properties of the flexible material to the skin itself, so that the sensor is as soft and flexible as real skin.

It’s a deceptively simple design,” says Abramson, “but these inherent advantages should be of great interest to the pharmaceutical and oncology communities. FAST could make the process of discovering cancer treatments much faster, more automated and cheaper,” he says.

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