Trace Detection and Speed - the New Name of the Game

FORT BELVOIR, VA, UNITED STATES

02.07.2017

Courtesy Story

Defense Threat Reduction Agency's Chemical and Biological Technologies Department

Fort Belvoir, VA - Some toxic chemicals, such as the deadly nerve agent Sarin, are colorless and odorless, but have debilitating effects within seconds. As our adversaries become more technologically sophisticated in using chemical and biological weapons, warfighters must be able to react to threats before effects emerge, making rapid single-molecule detection imperative.

Researchers funded by the Defense Threat Reduction Agency’s Joint Science and Technology Office are now developing advanced electrochemical techniques for real-time detection of low concentrations of biological threats. Early trace-level detection is the new name of the game, making identification of a single molecule possible using simple and rapid detection devices critical for increased warfighter safety.

Researchers from the University of Texas and the University of Washington aim to improve detection thresholds and sensitivity levels of chemical sensors by using a new technique to study the rates of chemical reactions of electrical processes, also known as collision electrochemistry. Using this method, researchers employ a microelectrode to detect collisions of nanoparticles with the electrode surface.

The collisions, which are typically due to changes in electrical current, are used for chemical sensing applications if the current transients are correlated to a target. To do this, both the nanoparticles and electrodes must be modified with molecular recognition entities, such as antibodies or DNA.

Using this technique, a single molecule is translated into an observable signal through an indicator reaction. In other words, there is a high degree of amplification in which a catalytic nanoparticle produces oxidation or reduction reactions at the electrode surface.

In the combined university experiments, researchers used collision electrochemistry to detect real-time occurrences of DNA mutations. For this proof-of-concept experiment, the team utilized DNA as a generic biological target to sense specific sequences that function as tumor biomarkers.

Researchers modified a gold (Au) microelectrode with a monolayer of single-stranded DNA (ssDNA) and introduced a solution of hydrazine (N2H4) to the new ssDNA microelectrode. The microelectrode was held at a potential where oxidation of N2H4, the indicator reaction, did not occur due to slow kinetics.

However, when platinum (Pt) nanoparticles modified with ssDNA complementary to the monolayer on the electrode surface are introduced into the microchannel, they may hybridize. This brings the platinum nanoparticles into close proximity to the electrode. Since platinum is catalytic for N2H4 oxidation, bursts of current are observed.

This new approach is highly versatile and detects tumor microRNA, or cellular RNA fragments. Detection of over-under expression is important for early cancer diagnosis, as microRNAs associated with cancerous tumor growth are dysregulated. These new findings remove previously encountered barriers.

Although the proof-of-concept used tumor biomarkers, researchers demonstrated that electrochemical collision science may be a viable technology for enhanced chemical sensing techniques for warfighters, allowing more accurate detection of chemical threats to mitigate exposure risks.

POC: Dr. Kiki Ikossi; [e-mail]

• Date Taken: 02.07.2017
• Date Posted: 02.07.2017 12:49
• Story ID: 222770
• Location: FORT BELVOIR, VA, US