ECHO probes: Fluorescence emission control for nucleic acid imaging

The understanding of the regulation of the mechanisms via which genomic information dictates cellular behaviors has become a great challenge of the postgenomic era. Tools that allow sensitive, quantitative, and real-time detection of specific transcripts, as well as the study of spatiotemporal gene regulation in living cells, are being developed. In this article, we review recent advances in nucleic acid detection using exciton-controlled hybridization-sensitive fluorescent oligonucleotide (ECHO) probe technologies. In ECHO probes, a hybridization-dependent fluorescent nucleotide regulated by the H-aggregation of thiazole orange organic dyes (D ₅₁₄) is incorporated into specific sequence contexts and serves as fluorescent detection readout for target nucleic acids. Multicolor detection and auxiliary functional modules have been built into ECHO probes to accommodate a broad range of biological applications.