A fiber-optic microarray biosensor using aptamers as receptors.

A fiber-optic biosensor using an aptamer receptor has been developed for the measurement of thrombin. An antithrombin DNA aptamer was immobilized on the surface of silica microspheres, and these aptamer beads were distributed in microwells on the distal tip of an imaging fiber. A different oligonucleotide bead type prepared using the same method as the aptamer beads was also included in the microwells to measure the degree of nonspecific binding. The imaging fiber was coupled to a modified epifluorescence microscope system, and the distal end of the fiber was incubated with a fluorescein-labeled thrombin (F-thrombin) solution. Nonlabeled thrombin could be detected using a competitive binding assay with F-thrombin. The aptamer beads selectively bound to the target and could be reused without any sensitivity change. The fiber-optic microarray system has a detection limit of 1 nM for nonlabeled thrombin, and each test can be performed in ca. 15 min including the regeneration time.