ADAPTING SELECTED NUCLEIC-ACID LIGANDS (APTAMERS) TO BIOSENSORS

A flexible biosensor has been developed that utilizes immobilized nucl eic acid aptamers to specifically detect free nonlabeled non-nucleic a cid targets such as proteins. In a model system, an anti-thrombin DNA aptamer was fluorescently labeled and covalently attached to a glass s upport. Thrombin in solution was selectively detected by following cha nges in the evanescent-wave-induced fluorescence anisotropy of the imm obilized aptamer. The new biosensor can detect as little as 0.7 amol o f thrombin in a 140-pL integrated volume, has a dynamic range of 3 ord ers of magnitude, has an inter-sensing-element measurement precision o f better than 4% RSD over the range 0-200 nM, and requires less than 1 0 min for sample analysis. The aptamer-sensor format is generalizable and should allow sensitive, selective, and fast determination of a wid e range of analytes.