A fiber-optic biosensor using aptamer as receptors

Reagentless biosensor that can directly tranduce molecular recognition to optical signal should potentiate the development of sensor array for a wide variety of analytes. Nucleic acid aptamer can bind ligand tightly and specifically with conformational change of aptamer, and can be used as a receptor in biosenor. We have therefore developed a fiber-optic biosensor by aptamer connected with molecular beacon. Molecular beacons consist of an oligonucleotide sequence containing complementary sequence sections at either end. These two sequence containing segments base pair with each other to form a hairpin shaped loop structure, the fluorophore and quencher were attached at 5'- and 3'-end of molecular beacon respectively. When thrombin binding to the stem-loop of molecular beacon aptamer, the pseudoknot structure was interrupted, resulting in a release of fluorescence from quenching and a increase in fluorescence emission. This novel biosensor is capable of detecting thrombin over the range from 50 pg/ml to 200 pg/ml. We have demonstrate that the biosensor system in this project has a large potential and specific and sensitive. A similar strategy could be used to study other analytes such as protein and small molecules.