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Ingestible Sensors Measure Gases in Stomach, Gut

Ingestible gas-sensing capsule

Ingestible gas-sensing capsule (Peter Clarke, RMIT)

9 January 2018. Researchers in Australia created a sensing device packed in a standard-size drug capsule that measures gas concentrations in the digestive tract in real time. An engineering and medical team from Royal Melbourne Institute of Technology and Monash University, also in Melbourne, describes the device and a pilot test with humans in yesterday’s inaugural issue of the journal Nature Electronics.

The team led by RMIT engineering professor Kourosh Kalantar-zadeh is seeking better tools to understand the workings of the human gut, an area of increasing interest to medical practitioners and researchers. Among these interests are gases in the gut, which can provide indicators of digestive tract health and the body overall. These gases include hydrogen, carbon dioxide, methane, nitrogen, and oxygen, generated from swallowed air, as well as digestive enzymes and gut microbes interacting with unabsorbed food.

The tools currently available to monitor gut gases are limited, however, either to analysis of exhaled breath or fecal samples, or swallowed capsules connected by wires to capture the data. These methods, say the authors, either use indirect observations, or in the case of tethered capsules, are literally difficult for many people to swallow.

Kalantar-zadeh and colleagues designed an easy-to-swallow self-contained device that meets the pharmaceutical industry’s maximum size standards for capsules, measuring 26 millimeters in length and 9.8 millimeters across. The capsule is made of a biocompatible polymer, with a membrane at one end that blocks liquids, but allows gases to permeate and be read by sensors inside. The capsule’s electronics include sensors to measure oxygen, hydrogen, and carbon dioxide gases, as well as a heat sensor, microcontroller, and radio transmitter. Separate tests show the sensors could read hydrogen and oxygen within 0.2 percent, and carbon dioxide within 1 percent of independent measures.

After being swallowed, capsules transmit data every 5 minutes, captured by a handheld receiver, and relayed via Bluetooth to a mobile phone. The capsules are then retrieved after excreted by the users.

The researchers tested the device to prove the concept and feasibility with 6 volunteers, with one individual participating twice. The volunteers were asked to consume high- or low-fiber diets, to gauge the device’s ability to distinguish between these different conditions. All of the devices were recovered from participants, who displayed no ill effects from the tests.

The results show the sensors measure levels of the three target gases — oxygen, hydrogen, and carbon dioxide — in the stomach and gut, indicating they can monitor activities in these organs in real time. The findings suggest the device can detect and measure microbial activity through the gastrointestinal system as it happens, where before fecal samples were required.

A particularly interesting finding is the presence and activity of oxygen in the stomach and gut. Kalantar-zadeh says in a university statement sensors show the stomach releases oxidizing chemicals to break down compounds that stay in the stomach longer than expected, a protective mechanism not previously reported.

In addition, sensors found the presence of oxygen in the gut, in some cases. “Trials showed the presence of high concentrations of oxygen in the colon under an extremely high-fiber diet,” notes Kalantar-zadeh. “This contradicts the old belief that the colon is always oxygen free. This new information could help us better understand how debilitating diseases like colon cancer occur.”

Kalantar-zadeh and co-author Kyle Berean filed for a patent on the technology. Bearan and others are also forming Atmo Biosciences, an enterprise to take the device to market, including plans for larger-scale clinical trials, working with technology commercialization company Planet Innovation.

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