Tunable
Loading of Single-Stranded DNA on Gold Nanorods
through the Displacement of Polyvinylpyrrolidone
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Abstract
A quantitative
and tunable loading of single-stranded (ss-DNA)
molecules onto gold nanorods was achieved through a new method of
surfactant exchange. This new method involves the exchange of cetyltrimethylammonium
bromide surfactants for an intermediate stabilizing layer of polyvinylpyrrolidone
and sodium dodecylsulfate. The intermediate layer of surfactants on
the anisotropic gold particles was easily displaced by thiolated ss-DNA,
forming a tunable density of single-stranded DNA molecules on the
surfaces of the gold nanorods. The success of this ligand exchange
process was monitored in part through the combination of extinction,
X-ray photoelectron, and infrared absorption spectroscopies. The number
of ss-DNA molecules per nanorod for nanorods with a high density of
ss-DNA molecules was quantified through a combination of fluorescence
measurements and elemental analysis, and the functionality of the
nanorods capped with dense monolayers of DNA was assessed using a
hybridization assay. Core–satellite assemblies were successfully
prepared from spherical particles containing a probe DNA molecule
and a nanorod core capped with complementary ss-DNA molecules. The
methods demonstrated herein for quantitatively fine tuning and maximizing,
or otherwise optimizing, the loading of ss-DNA in monolayers on gold
nanorods could be a useful methodology for decorating gold nanoparticles
with multiple types of biofunctional molecules