MRICD develops chemical exposure field diagnostic system

From APG News: 

Drawing from the technology used by diabetics to monitor their glucose levels, Dr. Shane Kasten at the U.S. Army Medical Research Institute of Chemical Defense developed an ultra-portable, easy to use device to provide early warning of suspected exposure to a chemical warfare nerve agent. 

The ChemDx Test System is designed to inform both medical and commander decisions as to the timely use of medical countermeasures, thereby enhancing survivability of chemical casualties on the battlefield and lowering the burden on the medical response. A utility patent for the device was issued on February 9, 2021.

Dermal exposure to some chemical warfare nerve agents can have a latent or pre-symptomatic period. However, even prior to the development of overt signs and symptoms, the enzymatic activity of certain blood cholinesterase enzymes may become depressed following exposure. Specifically measuring the activity of acetylcholinesterase in the blood is an extremely sensitive method of determining whether an exposure to chemical nerve agents has occurred.

With the ChemDx Test System, the warfighter can, with minimal training, use a blood sample from a simple finger stick during this pre-symptomatic window to obtain a real-time assessment of acetylcholinesterase inhibition. As with a glucometer and glucose strips, the blood sample is applied to a specially configured test strip that has been inserted into the device for near real time determination of the level of acetylcholinesterase activity in circulation. An indication of potential exposure is displayed in less than 40 seconds. 

When Kasten began working at the MRICD in 2009, the need for a low burden, low complexity test system to provide indication of exposure prior to overt symptoms had already been identified as a technical gap. A few years later, a Department of Defense program was initiated to develop wearable sensors. Kasten says he was “immediately intrigued with this wearable idea, but knew the technical hurdles would be great.” 

He realized that a small handheld device could offer much of the same convenience as a wearable sensor while providing near real time assessment. Then while having dinner with his family at a fast food restaurant, Kasten observed an elderly woman quickly and easily test her glucose levels with a glucometer and test strips. This event also triggered memories of watching his sister use a glucometer daily to treat her diabetes.

“That’s the moment I realized the glucometer/test strip was the most viable diagnostic platform for real time, far forward indication of exposure, potentially guiding treatment with a medical countermeasure therapy,” says Kasten. 

Kasten received seed funding to begin developing the reagent formulation and prototypes of the test strips after showing his test strips to a Defense Threat Reduction Agency (DTRA) science and technology manager visiting the MRICD. A full project from DTRA in 2017 resulted in the successful demonstration of the capabilities of the first prototype test strips and custom potentiostat to confirm exposure through an acetylcholinesterase assessment prior to the appearance of symptoms.

In 2018 the Department of Defense made the decision to move the work to advanced development, which is being overseen by the Joint Program Executive Office for Chemical, Biological, Radiological and Nuclear Defense. An Other Transactional Authority contract was awarded to MRI Global for the development of prototypes, in partnership with the MRICD and Conductive Technologies Inc., and for sponsorship of the device’s approval through the Food and Drug Administration. 

Over the past year, the MRICD provided analytical performance assessment of two successive prototypes of the ChemDx test system. These studies included evaluating the accuracy, linearity, precision and limits of detection/quantitation, and identifying potential interfering substances.

Additionally, Kasten along with coworker Zachary Canter undertook feasibility efforts to determine whether the ChemDx test system capabilities could be expanded to indicate exposure to a synthetic opioid by detecting an opioid metabolite in biological specimens. The project is exploring materials than can provide the sensitivity, specificity and stability needed for a robust opioid sensor. Future work will continue to optimize the developed sensor, evaluate the sensor’s analytical performance and further integrate it into the ChemDx platform.

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