Use of a steroid cyclic disulfide anchor in constructing gold nanoparticle-oligonucleotide conjugates.

A new anchoring group is described for binding oligonucleotides to gold surfaces. On the basis of a ketal derived from 4,5-dihydroxy-1, 2 dithiane and epiandrosterone, it is easy to prepare and to link to oligonucleotides. Gold nanoparticle-oligonucleotide conjugates made using this cyclic disulfide linker serve as effective probes for detecting specific oligonucleotide sequences, and they exhibit much greater stability toward dithiothreitol than corresponding conjugates prepared with the conventional mercaptohexyl group or an acyclic disulfide unit. The high stability toward thiol deactivation likely results, in part at least, from anchoring each oligonucleotide to gold through two sulfur atoms.