Stanford University engineers have created a wearable sensor device that can be stuck to the skin to measure the changing size of tumors below. Known as FAST for “Flexible Autonomous Sensor Measuring Tumors”, the technology is a battery-operated device that can capture changes of one-hundredth of a millimeter (10 micrometers) in real time and provide these measurements via a smartphone app. . The sensor could provide an effective way to screen for cancer drugs. An article describing the device is published in Scientists progress.
Historically, preclinical studies in mice often involve tumors implanted subcutaneously under the skin of mice. “It allows you to test a ton of different tumor types and drugs in a very easily accessible tumor,” explained Alex Abramson, the study’s first author. “With FAST, we have developed a better way to measure how tumors are responding, overcoming the limitations of current electronics that are too large to be implanted or for tumors that must be measured by hand with calipers or by imaging with CT scans or bioluminescence.
These technologies can be labor intensive and time limited. “With this new technology, a sensor backpack is attached to the top of the mouse, allowing it to read measurements continuously in real time, giving us a data set that contains much more information than what you would get using an imaging system,” Abramson said. .
FAST’s sensor is made of a soft, stretchy, skin-like polymer that includes an embedded layer of gold circuitry. When this sensor is stretched, it develops small cracks which change the electrical conductivity of the material. Stretch the material and the number of cracks increases, which also leads to an increase in electronic resistance in the sensor. When the material contracts, the cracks come back into contact and the conductivity improves.
“People have been using gold patterns to connect flexible and expandable electronic interconnects for some time now,” Abramson said. “But what we’ve done is we’ve pre-stretched it a bit, about 30% to 50% more, which allows it to detect ultra-sensitive changes.” If a tumor grows, more cracks appear, forcing electrons to travel a convoluted pathway increasing resistance. Conversely, if the tumor shrinks, these cracks begin to reconnect, changing the conductivity of the sensor, allowing electrons to pass through more easily.
The sensor is connected to a small electronic backpack that measures the tension exerted on the membrane – how much it stretches or shrinks – and transmits this data to a smartphone. “The sensor gives us a real-time data set, which hasn’t been shown before,” Abramson added. “Because the sensor is ultra-sensitive down to 10 micrometers, taking measurements every five minutes, it allows us to read very, very small changes in tumor progression or regression almost the moment they occur. .” In experiments with mice, researchers were able to detect discernable differences in tumor volume dynamics within five hours of drug initiation.
Other studies have shown that the sensor can also wrap around a tumor, increasing the ability to measure changes in shape. The authors claim that the FAST packs are reusable with a cost of around $60 to assemble.
“We see the primary application of the FAST system is in the drug screening process,” Abramson said. “This would allow a fully automated version of drug screening that is not possible in animals at present, allowing many more drugs to be tested more efficiently with much less human effort.”
Abramson thinks FAST can also help researchers perform different types of experiments on different types of tumors. “For example, we would be able to know how the tumor is impacted in real time by very small doses continuously compared to a large dose at one time,” he adds.
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