A FIBER OPTIC BIOSENSOR FOR FLUOROMETRIC DETECTION OF TRIPLE-HELICAL DNA

A fiber optic biosensor was used for the fluorimetric detection of T/A T triple-helical DNA formation, The surfaces of two sets of fused sili ca optical fibers were functionalized with hexaethylene oxide linkers from which decaadenylic acid oligonucleotides were grown in the 3' to 5' and 5' to 3' direction, respectively, using a DNA synthesizer, Fluo rescence studies of hybridization showed unequivocal hybridization bet ween oligomers immobilized on the fibers and complementary oligonucleo tides from the solution phase, as detected by fluorescence from interc alated ethidium bromide, The complementary origonucleotide, dT(10), wh ich was expected to Watson-Crick hybridize upon cooling the system bel ow the duplex melting temperature (T-m), provided a fluorescence inten sity with a negative temperature coefficient, Upon further cooling, to the point where the pyrimidine motif TAT triple-helix formation occu rred, a fluorescence intensity change with a positive temperature coef ficient was observed, The reverse-Hoogsteen. T.AT tripler, which is kn own to form with branched nucleic acids, provided a corresponding decr ease in fluorescence intensity with decreasing temperature, Full analy tical signal evolution was attainable in minutes.