SURFACE-PLASMON RESONANCE IMAGING MEASUREMENTS OF DNA HYBRIDIZATION ADSORPTION AND STREPTAVIDIN DNA MULTILAYER FORMATION AT CHEMICALLY-MODIFIED GOLD SURFACES/

A combination of scanning and imaging surface plasmon resonance (SPR) experiments is used to characterize DNA hybridization adsorption at go ld surfaces and the subsequent immobilization of streptavidin. Single- stranded oligonucleotides are immobilized at gold surfaces, and the hy bridization of biotinylated complements from solution is monitored wit h SPR. The subsequent attachment of streptavidin to the biotinylated c omplements provides a method of enhancing the SPR imaging signal produ ced as a result of the hybridization and leads to a 4-fold improvement in the hybridization detection limit of the SPR imaging apparatus. In situ scanning SPR experiments are used to measure a 60 +/- 20% hybrid ization efficiency between immobilized single-stranded DNA and biotiny lated complements. From the information provided by both the in situ i maging and scanning SPR experiments, an absolute surface coverage of i mmobilized single-stranded DNA is estimated to be similar to 3 x 10(12 ) molecules/cm(2). The SPR signal resulting from hybridization onto im mobilized probes is further amplified by the formation of streptavidin /DNA multilayers which grow by a combination of DNA hybridization and biotin-streptavidin binding. DNA/DNA multilayers without streptavidin are used as an additional method of amplifying the SPR signal.