New wearable device measures changes in tumor size under the skin

Engineers at Stanford University have created tiny autonomous devices with stretchy and flexible sensors that can be attached to the skin to measure changes in the size of underlying tumors. The non-invasive, battery-powered device has a sensitivity of 1/100th of a millimeter (10 micrometers) and can wirelessly transmit real-time results to a smartphone app with the push of a button.

In fact, the researchers say their device, called FAST, a “flexible autonomous sensor that measures tumors,” is an entirely new, fast, cheap, hands-free way to test the efficacy of anticancer drugs. expresses the exact method. On a larger scale, it could lead to promising new directions in cancer therapy. FAST is described in detail in a paper published on September 16th. scientific progress.

Each year, researchers test thousands of potential cancer drugs in mice with subcutaneous tumors. The process of finding new treatments is slow because few reach human patients, and techniques that measure tumor regression with drug treatments take weeks to read responses. Inherent biological variability in tumors, shortcomings of existing measurement approaches, and relatively small sample sizes make drug screening difficult and laborious.

“Sometimes we have to manually measure the tumor under observation with a vernier caliper,” he says. Alex Abramsonthe first author of the study and a recent postdoctoral fellow in the lab Zhenan BaoKK Lee Professor of Chemical Engineering, Stanford School of Engineering.

The use of metal pliers-like calipers to measure soft tissue is not ideal, and radiological approaches cannot provide the kind of continuous data needed for real-time assessment. FAST can detect changes in tumor volume on a timescale of minutes, whereas caliper and bioluminescence measurements often require observation periods of several weeks to read changes in tumor size.

power of gold

FAST’s sensor is composed of a flexible, stretchable, skin-like polymer with an embedded layer of gold circuitry.The sensor is attached to a small electronic backpack designed by a former postdoc and co-author Yasser Khan When Naoji MatsuhisaThe device measures the strain (how much it stretches or shrinks) of the membrane and sends that data to your smartphone. Using the FAST Backpack, therapies that may be associated with tumor size reduction can be quickly and confidently ruled out as ineffective and quickly followed for further study. increase.

Researchers say the new device offers at least three important advances, based on studies with mice. First, the sensor is physically attached to the mouse and remains in place for the entire duration of the experiment, thus providing continuous monitoring. Second, because the flexible sensor wraps around the tumor, it can measure shape changes that would otherwise be difficult to discern. Third, FAST is autonomous and non-invasive. It attaches to your skin like a bandage, runs on batteries, and connects wirelessly. The mouse can move freely, unhindered by devices or wires, and scientists do not have to actively handle the mouse after sensor placement. FAST packs are reusable, cost as little as $60 to assemble, and attach to your mouse in minutes.

The breakthrough lies in FAST’s flexible electronic materials. A layer of gold is coated over a skin-like polymer that, when stretched, develops tiny cracks that change the electrical conductivity of the material. The material stretches, the number of cracks increases, and the electronic resistance of the sensor also increases. As the material shrinks, the cracks reconnect and become more conductive.

Abramson and co-author Matsuhisa (Associate Professor, University of Tokyo) characterized how these crack propagation and exponential changes in conductivity are mathematically equivalent to changes in dimension and volume.

One hurdle the researchers had to overcome was the concern that the sensor itself could exert excessive pressure on the tumor, effectively squeezing it, thereby compromising the measurements. To avoid that risk, they carefully matched the mechanical properties of the flexible material to the skin itself, making the sensor supple and supple like real skin.

“Despite its deceptively simple design, these inherent advantages should be of great interest to the pharmaceutical and oncology communities. may be reduced.”