Label-free probing of the binding state of DNA by time-domain terahertz sensing

We present a promising approach for the label-free characterization of gene tic material. Time-resolved terahertz (THz) transmission analysis of polynu cleotides demonstrate a strong dependence of the complex refractive index o n the binding state (hybridized/denatured) of deoxyribonucleic acid (DNA) m olecules. By monitoring THz transients, one can thus infer the binding stat e of oligo- and polynucleotides, and hence identify polynucleotides by dete cting the binding of unknown polynucleotide DNA sequences to known probe mo lecules. A broadband experimental demonstration in a free-space configurati on, as well as a discussion of the potential application for next generatio n gene chips is presented. (C) 2000 American Institute of Physics. [S0003-6 951(00)01551-5].