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Mohammad Ali1 Tsung-Han Tsai1 MinHo Yang1 Paul Braun1

1, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States

Highly toxic chemical warfare agents (CWAs) such as sarin and related compounds possess potential threats at trace concentration, however, detection as low as Acute Exposure Guideline Levels (AEGLs) tier 1 (6.9 × 10-09 mg/cm3 for 10 min) remains a challenge. Extensive efforts have been made to develop signal amplification technique for early detection of biological and chemical species. We previously reported that chemical gradients in hydrogel films can concentrate molecule at least 40-fold (by 24 h) by biasing diffusion. While we believe the concept of gradient-directed transport is attractive, and enhances the sensor response, however the slow transport velocity limits the applicability for real time detection. In this work, we propose a novel method in which a target molecule is fragmented by a catalyst into small parts and a specific small fragmented specie is directionally transported via imbedded chemical gradient in gel to a small-sized sensor (integrated in the gel). Since the small fragmented specie diffuses considerably faster than the original molecule, this method should accelerate the low velocity of the molecular transportation by at least two-orders of magnitude. For a proof of concept measurement, we will demostrate that an aerosol deposited sarin simulant, diisopropyl fluorophosphates (DFP) absorbs in a hydrogel and subsequently hydrolyzes upon contact with imbedded enzyme, diisopropyl fluorophosphatase (DFPase), producing F-. The F- is then concentrated via a built-in ionic chemical gradient to a miniature electrochemical sensor, thus giving 30-fold amplified respond within 10 minutes. This method allows us to detect airborne sarin as low as tier-1 AEGLs and opens a new detection platform for other potentially dangerous chemical and biological agents at very low concentration before they have done too much harm.

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