Core-gap-shell Au nanotags with size-controlled loading capacity via oligonucleotide anchors

Herein, we propose a modified synthetic protocol for obtaining gold nanocomposites with a core-shell structure and a gap of adjustable thickness. To obtain nanocomposites of this type, a multi-step synthetic approach has been developed, based on the fabrication of Au nanoparticle templates (core) with regarded diameters ranging from 15 nm to 35 nm, followed by functionalization of with single-stranded DNA oligonucleotides (ssDNA) acting as spacers, and subsequent coating with a secondary Au shell. Adjustment of the thickness of the formed gap in the range from 2 nm to 6 nm is achieved by using oligonucleotide spacers of various lengths, from 5 nucleobases to 40 nucleobases. The developed core-gap-shell Au nanotags possess a modality to load various bioligands, such as fluorescent labels, Raman reporters, drug molecules etc, with exceeded capacity. The coating with a thin 20–35 nm secondary gold shell protects the embedded ligands while preserving their native properties and bioactivity. The fabricated nanocomposite particles can be further modified via standard labeling procedures as for typical gold nanoparticles, which makes them attractive candidates as multi-modal labels for genetic and immunochemical test systems.