A fiber optic immunosensor has been developed for simultaneous detection of
the most common explosives, 2,4,6, trinitrotoluene (TNT) and hexahydro-1,3
,5-trinitro-1,3,5-triazine (RDX). It employs a competitive immunoassay on t
he antibody-coated fiber optic probes, in which a fluorescent antigen compe
tes with free antigen of unknown concentration for binding sites on the fib
er surface. To achieve dual explosive detection, two alpha-TNT fiber probes
and two alpha-RDX fiber probes are connected in series. The sample is mixe
d with fluorescent analogs, Cy5-ethylenediamine-trinitrobenzene (Cy5-EDA-TN
B) and Cy5-ethylenediamine-RDX hapten (Cy5-EDA-RDH). Inhibition of the maxi
mum signal in the presence of the sample is proportional to the concentrati
on of the explosive. The detection limits for the multi-analyte assays are
equivalent (6 ng/ml for both TNT and RDX) to those of the individual assays
(5 ng/ml for both TNT and RDX). The standard curves for TNT and RDX repres
ent a Linear relationship between percent signal inhibition and the natural
logarithm of analyte concentration in the multi-analyte format, as well as
in single analyte assays, thus allowing a simple and precise method of qua
ntification. There is minimal cross-reactivity for the two antigens in the
multi-analyte immunosensor, so it is also an effective means in analyzing s
amples containing mixtures of RDX and TM: (C) 1999 Elsevier Science B.V. Al
l rights reserved.