Vapor-Phase Substrate Nitroreductase Reaction and Its Application as TNT Electrochemical Gas Sensor

Nitroreductase (NTR) is an enzyme that specifically reduces nitroaromatic activity. Some nitroaromatic explosives are exploited by terrorists. Among these highly explosive materials, 2,4,6-trinitrotoluene (TNT) is often used, which makes the detection of TNT an important research topic in the fight against terrorism. TNT vapor detection by gas sensor is an approach that has been under active investigation for several years. Despite this effort, presently, there is limited practical success, in part, due to the ultralow volatility nature of TNT. In this work, we propose an application of the NTR reaction in a hydrogel gas sensor to detect TNT vapor. First, NTR activity in the hydrogel was confirmed by adding TNT and 2,4-dinitrotoluene (DNT) solutions to the NTR-hydrogel sensor conducting cyclic voltammetry (CV) experiments. Then, further CV experiments were carried out with gas phase samples. The CV graphs of NTR-hydrogels detecting vapors containing the explosive substrates and negative controls were compared. Results showed that the signal from the nitroaromatics increased with exposure time, where the TNT signal was the highest of all tested compounds. The gas sensor was sensitive enough to detect TNT gas presented in an ambient air at room temperature.