Rapid, on-site testing for RDX

Aptamer-based biosensor measures the amount of toxin in soil and water


The plastic explosive known as C-4 is approximately 91 percent RDX. (Kathryn Whittenberger/Navy)

Since World War II, the plastic explosive known as C-4 has been widely used for military and civilian operations, e.g., excavation and demolition. C-4 contains the explosive cyclotrimethylenetrinitramine, also known as cyclonite or RDX, which is an environmental contaminant that can leach through soils and foul underlying groundwater aquifers.

RDX is toxic to humans and has been shown to cause convulsions, nausea, vomiting, short-term confusion, and has been indicated for toxic encephalopathy. RDX has also been used commercially as rat poison.

The EPA has identified more than 30 RDX contaminated sites in the United States and listed them as national cleanup priorities.

Testing for the presence of RDX in areas of known use of C-4 and other explosives is important although there are several problems with making accurate measurements of contamination. RDX concentrations vary across and within soil thus requiring a high number of samples from discrete locations. Current RDX testing methods require the use of highly sensitive and expensive, laboratory-based instrumentation to separately test each sample. This type of high-sensitivity, off-site testing is not appropriate for a large-scale government or private environmental cleanup project and does not yield the necessary data for evaluating dispersal patterns over a contaminated site.

For improved planning and remediation, Army scientists have developed a new method of detecting RDX that addresses deficiencies. Detection occurs by one or more synthetic RNA aptamers designed to bind RDX with high sensitivity and selectivity. Binding of RDX by the aptamers may be assessed via chromatographic or enzymatic immunoassay techniques. Alternatively, one or more aptamers may be incorporated within a biosensor device wherein the RDX specific aptamers are linked to electrodes. Binding creates a current change, which is measured by a potentiostat. The amplitude of the measurement is correlated with the concentration of RDX. The biosensor solution allows for on-site testing, which greatly diminishes costs and speeds results.

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