Single bio-molecule detection with quantum dots in a microchannel

This paper describes a novel method for identifying specific biomolecules at the single-molecule level. The detection principle is based on spatial and temporal coincidence of fluorescent emissions from two quantum dot (QD)-labeled probes specifically bound to a target biomolecule and detected by a single wavelength-excitation, dual-emission confocal fluorescence spectroscopic system. A variety of probe molecules including oligonucleotides, antibodies, and ligands can be labeled with QDs for detecting different biomolecules, rendering this a generic method of molecular identification. Specific detection of both DNA and protein at the single-molecule level is presented. Fluorescent colloidal nanobeads are demonstrated as alternative effective fluorescent tags for the application of coincidence detection. Measurement with high signal-to-noise ratio is achieved by performing single-molecule detection in a microchannel with proper flow-rate control.