DNA aptamers as radically new recognition elements for biosensors

A fiber-optic biosensor based on DNA aptamers used as receptors was developed for the measurement of thrombin concentration. Anti-thrombin DNA aptamers were immobilized on silica microspheres, placed inside microwells on the distal tip on an imaging optical fiber, coupled to a modified epifluorescence microscope through its proximal tip. Thrombin concentration is determined by a competitive binding assay using a fluorescein-labeled competitor. The biosensor is selective and can be reused without any sensitivity change. The thrombin limit of detection is 1 nM, sample volume is 10 l, and assay time per sample is 15 min including the regeneration step.