Interfacial Au nanoparticle decoration of a disulfide modified G-wire

The guanine-rich oligonucleotide (GRO), dGGGGTTGGGG (G₄T₂G₄), has the capacity to form a linear supramolecular polymer known as a G-wire. Individual nucleotides of the component GROs can be functionally modified to serve as site-specific attachment points in the G-wire while not interfering with its self-assembling properties. An amine linker modification to an internal thymine base of the GRO, denoted G₄TT*G₄, serves as a chemically versatile attachment site.

In this work, addition of an alkyl disulfide to G₄TT*G₄ produces the GRO G₄TT^dG₄ enabling binding to gold nanoparticles via place exchange chemistry. G-wires assembled by combining G₄T₂G₄ and G₄TT^dG₄ were stably maintained in an aqueous environment. Disulfide modified G-wires (DS_G-wire) were then covered with dodecanethiol capped gold nanoparticles in an organic solvent via an interfacial place exchange reaction. Tapping Mode AFM and TEM were used to image G-wires decorated with gold nanoparticles. The specificity of the interfacial place exchange reaction was measured using a fluorometric dye displacement from the gold nanoparticles.

The results show that a two component DS_G-wire with an amphipathic tether readily self-assemble as shown by PAGE and TM-AFM. The amphipathic disulfide moiety of DS_G-wires facilitates place exchange chemistry with alkylthiol protected Au nanoparticles across an aqueous-organic interface.

Interfacial place exchange is an effective strategy for decorating DS_G-wires with Au nanoparticles.

The use of modified G-wire self-assembly combined with a high degree of nanoparticle binding specificity presents another strategy for the use of G-wires as a rigid one-dimensional molecular scaffold with potential applications in nanoscale device construction. This article is part of a Special Issue entitled "G-quadruplex" Guest Editor: Dr. Concetta Giancola and Dr. Daniela Montesarchio.