A fiber optic biosensor for multianalyte detection: importance of preventing fluorophore aggregation

Individual assays for the detection of the explosives hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and 2,4,6,-trinitrotoluene (TNT) with a fiber optic biosensor have been developed in our laboratory. The next step is to develop an assay for simultaneous detection of RDX and TNT, To obtain this goal, a mixture of the fluorescently-labeled analogs Cy5-EDA-RDH and Cy5-EDA-TNB used in the individual assays is run over anti-RDX and anti-TNT fiber probes connected in series. There is an increased total fluorophore concentration in the mixture which results in a significant increase in the normalized signal compared to that produced by a single fluorophore. Aggregation of the amphiphilic fluorophores in the mixture on the surface of the fiber optic probe is a possible reason for the observed effect. We explored the use of nonionic (Tween 20) and ionic detergents (deoxycholic acid) to block aggregate formation and allow analytical determination of RDX and TNT. Conditions are reported under which this is possible. (C) 1998 Elsevier Science S,A. All rights reserved.