Abstract
Buried explosive material, e.g., landmines, represent a severe issue for human safety all over the world. Most explosives consist of environmentally hazardous chemicals like 2,4,6-trinitrotoluene (TNT), carcinogenic 2,4-dinitrotoluene (2,4-DNT) and related compounds. Vapors leaking from buried landmines offer a detection marker for landmines, presenting an option to detect landmines without relying on metal detection. 2,4-Dinitrotoluene (DNT), an impurity and byproduct of common TNT synthesis, is a feasible detection marker since it is extremely volatile. We report on the construction of a wireless, handy and cost effective 2,4-dinitrotoluene biosensor combining recombinant bioluminescent bacterial cells and a compact, portable optical detection device. This biosensor could serve as a potential alternative to the current detection technique. The influence of temperature, oxygen and different immobilization procedures on bioluminescence were tested. Oxygen penetration depth in agarose gels was investigated, and showed that aeration with molecular oxygen is necessary to maintain bioluminescence activity at higher cell densities. Bioluminescence was low even at high cell densities and 2,4-DNT concentrations, hence optimization of different prototypes was carried out regarding radiation surface of the gels used for immobilization. These findings were applied to sensor construction, and 50 ppb gaseous 2,4-DNT was successfully detected.
Highlights
Many explosive remnants of current and past armed conflicts can be still found today scattered all over the world
Liquid culture of the bacterial bioreporter−1(OD600 = 5) was transferred the cuvette, aeration with molecular oxygen was started (5 mL∙min −)1 and bioluminescence was into the cuvette, aeration with molecular oxygen was started (5 mL·min ) and bioluminescence was measured continuously using a fluorescence spectrophotometer (Figure 2)
Production of luciferase is induced by 2,4-DNT and the emitted bioluminescence is measured by a photodiode, integrated into a specially designed sensor chamber the size of a beverage can
Summary
Many explosive remnants of current and past armed conflicts can be still found today scattered all over the world. It is estimated that there are over 110 million landmines in 70 different countries [1]. Anti-personnel landmines are cheap and no expertise is required for their simple deployment [1,2]. Safe and robust detection methods are necessary to find and remove the explosives. The most common method is the use of a metal detector which is basically unchanged since its invention in 1943. A lot of modern mines are made of plastic revealing the major drawback of this detection strategy, since it indirectly detects not the explosive itself but only the mine’s housing. Detection using a metal detector is limited and should be replaced with a safer and modern approach which targets the explosive chemical itself [3]
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