UV-FIA: UV-induced fluoro-immunochemical assay for ultra-trace detection of PETN, RDX, and TNT.

Fluorescence quenching based immunoassay format for the detection of a trace amount of some nitro-explosives with a high degree of selectivity is reported in this study. The immunoassay comprises anti-explosive antibodies functionalized microtitre strips specific to the targeted explosives, pentaerythritol tetranitrate (PETN), 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), and 2,4,6-trinitrotoluene (TNT). UV induced photolysis of nitro-explosive bound to targeted antibodies generates primarily nitrite ions which after the quick reaction with the detector molecule, 2,3-diaminonaphthalene (DAN), a fluorophore, quenches its fluorescence intensity, however, proportionately undergo cyclization to produce a highly fluorescent product, 2,3-naphthotriazole (NAT). The synthesized product, NAT, was verified using various chromatographic and spectrophotometric techniques. This newly developed antibody-based detection method, utilizing DAN dye, demonstrated a high selectivity towards PETN, RDX, and TNT. This method can be used as an economical testing kit for direct quantification of explosives, implying the great potential for quick, low-cost trace detection of explosives.

Development of highly sensitive and selective antibodies for the detection of the explosive pentaerythritol tetranitrate (PETN) by bioisosteric replacement.

An improved antibody against the explosive pentaerythritol tetranitrate (PETN) was developed. The immunogen was designed by the concept of bioisosteric replacement, which led to an excellent polyclonal antibody with extreme selectivity and immunoassays of very good sensitivity. Compounds such as nitroglycerine, 2,4,6-trinitrotoluene, 1,3,5-trinitrobenzene, hexogen (RDX), 2,4,6-trinitroaniline, 1,3-dinitrobenzene, octogen (HMX), triacetone triperoxide, ammonium nitrate, 2,4,6-trinitrophenol and nitrobenzene were tested for potential cross-reactivity. The detection limit of a competitive enzyme-linked immunosorbent assay was determined to be around 0.5 µg/l. The dynamic range of the assay was found to be between 1 and 1000 µg/l, covering a concentration range of three decades. This work shows the successful application of the bioisosteric concept in immunochemistry by exchange of a nitroester to a carbonate diester. The antiserum might be used for the development of quick tests, biosensors, microtitration plate immunoassays, microarrays and other analytical methods for the highly sensitive detection of PETN, an explosive frequently used by terrorists, exploiting the extreme difficulty of its detection.