FIBER OPTIC BIOSENSOR FOR FLUOROMETRIC DETECTION OF DNA HYBRIDIZATION

Single stranded deoxyribonucleic acid (ssDNA) thymidylic acid icosanucleotides (dT20) were grown onto optical fibers. The fibers were first derivatized with gamma-aminopropyltriethoxysilane (APTES) onto which a spacer arm of 1,10 decanediol bis-succinate terminated with 5'-O-dimethoxytrityl-2'-deoxythymidine was covalently attached. The synthetic route used to grow the ssDNA was the well established solid-phase phosphoramidite methodology. The covalently immobilized oligomers were able to hybridize with available complementary ssDNA (cDNA) which was introduced into the local environment to form double stranded DNA (dsDNA). This event was detected by the use of the fluorescent DNA stain ethidium bromide (EB). The sampling configuration utilized total internal reflection of optical radiation within the fiber, resulting in an intrinsic mode optical sensor. The non-optimized procedure used standard hybridization assay techniques to provide a detection limit of 86 ng ml-1 cDNA, a sensitivity of 83% fluorescence intensity increase per 100 ng ml-1 of cDNA initially present, with a hybridization analysis time of 46 min. The sensor has been observed to sustain activity after prolonged storage times (3 months) and harsh washing conditions (sonication).