Plasmonic assemblies of gold nanorods on nanoscale patterns of poly(ethylene glycol): Application in surface-enhanced Raman spectroscopy

Abstract

Approaches are needed for the tailored assembly of plasmonic building blocks on the surface of substrates to synergistically enhance their properties. Here we demonstrate selective immobilization and assembly of gold nanorods (NRs) on substrates modified and patterned with end-grafted poly(ethylene glycol) (PEG) layers. The ligand exchange from the initial cetyltrimethylammonium bromide to sodium citrate was necessary for the immobilization of gold NRs onto PEG grafted substrates. Linear nanopatterns of PEG were fabricated using electrospun nanofibers as masks in oxygen plasma etching. The selective immobilization of citrate-stabilized gold NRs with a length of ∼50 nm and a width of 20 nm on the nanopatterned PEG layers led to linear and registered arrays of rods. The number of gold NRs per line depended on the width of the patterns and approached 1 when the width of the patterns was comparable to the length of the rods. The confinement of the binding regions led to a ∼3 fold increase in the number of gold NRs immobilized per unit area. The selective and dense immobilization of gold NRs on the nanoscale patterns of PEG resulted in spatially defined and strong surface-enhanced Raman scattering activity enabling detection of molecules at concentrations as low as 1 nM.

Engineered Gold-Based Nanomaterials: Morphologies and Functionalities in Biomedical Applications. A Mini Review

“…As is well known, morphology plays a key role in gold-nanotechnology, especially in relation to the possibility of having materials with different symmetries (spheres, rods, and cubes) [1,2,3,4,12,24,28,70,71,72,73,74] or without a defined and reproducible symmetry (stars, hollow particles, and cages) [1,75,76,77,78,79,80,81,82,83,84]. Highly symmetrical particles are the most studied because of their low dispersity and synthetic reproducibility, which assure the repeatability of experiments and results.…”

“…The spherical AuNPs and their composites are widely applied in therapy, diagnostics, drug/gene delivery and sensors [39,70,73,85,100,106,108]. For example, a NIR-triggered, controlled-release system, based on Au/silica core–shell nanospheres, is prepared to study the release of urokinase plasminogen activators.…”

“…The AuNRs’ self-assembly can be induced by DNA, both in one- and two-dimensional structures, using specific experimental conditions: (i) a proper aspect ratio, (ii) DNA concentration, and (iii) electrostatic interaction (between the positively charged nanorod surface and the negatively charged DNA surface). Additionally, ternary compounds can be obtained when the CTAB-coated AuNRs were mixed directly with DNA [10,73]. Another general strategy to achieve biocompatible materials is the functionalization by means of polyethylene glycol (PEG).…”

“…AuNRs are involved in many biomedical applications, from imaging to therapy to biosensors [2,31,73,120]. For example, CTAB-coated AuNRs were functionalized with polyethylene glycol (PEG) and (BSA), and loaded with an immunoadjuvant imiquimod.…”

Highly Hydrophilic Gold Nanoparticles as Carrier for Anticancer Copper(I) Complexes: Loading and Release Studies for Biomedical Applications

“…Moreover, AuNPs present optical properties, which can be easily tuned to desirable wavelengths according to their shape (e.g., nanoparticles, nanoshells, nanorods, etc. ), size (e.g., 1 to 100 nm) and composition (e.g., core/shell or alloy noble metals) [16,17,18,19,20], enabling their imaging and photothermal applications [21,22,23,24,25,26]. AuNPs can also be easily functionalized with different moieties, such as antibodies, peptides and/or DNA/RNA to specifically target different cells [10,27,28], and with biocompatible molecules to prolong their in vivo circulation for drug delivery applications [29,30].…”