A capillary biosensor developed by researchers at the Naval Research Laboratory in Washington and the State University of New York in Binghamton displays a detection limit of 30 to 50 pg/ml, thanks to integrating waveguiding in the capillary. The design, which the team describes in the Feb. 1 issue of Analytical Chemistry, promises to simplify bioassays.In the new system, the light from the excitation source passes through an optical chopper and a line generator so that it exposes the length of the capillary. The capillary integrates any fluorescent signal from the tagged capture antibody and guides it to the end of the structure for capture and analysis.