Oligonucleotide-capped gold nanoparticles for improved atomic force microscopic imaging and enhanced selectivity in polynucleotide detection

A novel assay for selective determination of polynucleotides using atomic f orce microscopy in conjunction with the formation of the probe/target/DNA-g old nanoparticle sandwich structure at a gold surface is described. A 17-me r probe was attached to the surface for subsequent hybridization with a pol ynucleotide target. Due to the flat orientation of the probe-target hybrid with respect to the surface and the spatial obstruction of the unhybridized probes near the hybrids, the AFM images are not clear. The hybridization e fficiency was estimated to be about 1.1% since certain surface features cou ld not be resolved. The utilization of 30-mer-capped gold nanoparticles not only provides another dimension of selectivity, but also reorients the pre viously formed probe-target hybrid in such a way that the strands of the ta rget become tethered with respect to the surface. This reorientation improv es the resolution in imaging the hybridized target molecules and provides a n accurate determination of the hybridization efficiency (16%). (C) 2000 Ac ademic Press.