FIBER OPTIC BIOSENSOR FOR FLUOROMETRIC DETECTION OF DNA HYBRIDIZATION

Single stranded deoxyribonucleic acid (ssDNA) thymidylic acid icosanuc leotides (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-dime thoxytrityl-2'-deoxythymidine was covalently attached. The synthetic r oute used to grow the ssDNA was the well established solid-phase phosp horamidite methodology. The covalently immobilized oligomers were able to hybridize with available complementary ssDNA (cDNA) which was intr oduced into the local environment to form double stranded DNA (dsDNA). This event was detected by the use of the fluorescent DNA stain ethid ium bromide (EB). The sampling configuration utilized total internal r eflection of optical radiation within the fiber, resulting in an intri nsic mode optical sensor. The non-optimized procedure used standard hy bridization assay techniques to provide a detection limit of 86 ng ml- 1 cDNA, a sensitivity of 83% fluorescence intensity increase per 100 n g ml-1 of cDNA initially present, with a hybridization analysis time o f 46 min. The sensor has been observed to sustain activity after prolo nged storage times (3 months) and harsh washing conditions (sonication ).