title: Trace level detection of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by microimmunosensor.
abstract: Reported in this paper is the development and characterization of a highly sensitive microcapillary immunosensor for the detection of the explosive, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). The immunosensor exploits antibodies as recognition elements for target antigens, fluorescence dye conjugates for reporter molecules and fused silica microcapillaries for its high surface-to-volume ratio. Detection of RDX with the microcapillary immunosensor requires covalent immobilization of anti-RDX antibodies on the inner core of the microcapillaries via heterobifunctional cross-linker chemistry. Subsequent saturation of all antibody binding domains follows with a synthetically prepared fluorescent analog of RDX. Displacement immunoassays were performed with the microcapillary immunosensor with the injection of unlabeled RDX at concentration levels from 1 part-per-trillion (pptr) to 1000 part-per-billion (ppb). As unlabeled RDX reaches the binding domain of the antibody, fluorescent RDX analog is displaced from the antibody, flows downstream and is measured by a spectrofluorometer. Fluorescence measurements of the displaced fluorescent RDX analog were equated to a standard calibration curve to quantify sample concentration. Complete evaluation of the RDX microcapillary immunosensor for selectivity and sensitivity was performed based on the following criteria: variable flow rates, antibody cross-reactivity, reproducibility and cross-linker (carbon spacer) comparison. Results indicate the lowest detectable limit (LDL) for RDX is 10 pptr (ng/l) with a linear dynamic range from 0.1 to 1000 ppb (ug/l).
authors.affiliation: Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC 20375-5348, USA.
authors.forename: P T
authors.initials: PT
authors.lastname: Charles
authors.forename: A W
authors.initials: AW
authors.lastname: Kusterbeck
mesh_terms: D015374:Biosensing Techniques; D003429:Cross Reactions; D003432:Cross-Linking Reagents; D007118:Immunoassay; D008832:Microchemistry; D015203:Reproducibility of Results; D012212:Rheology; D014227:Triazines / Q000032:analysis*
chemical_list: D003432:Cross-Linking Reagents; D014227:Triazines; C009160:cyclonite