Plasmonic Nanoassemblies: Tentacles Beat Satellites for Boosting Broadband NIR Plasmon Coupling Providing a Novel Candidate for SERS and Photothermal Therapy

Abstract

Optical theranostic applications demand near‐infrared (NIR) localized surface plasmon resonance (LSPR) and maximized electric field at nanosurfaces and nanojunctions, aiding diagnosis via Raman or optoacoustic imaging, and photothermal‐based therapies. To this end, multiple permutations and combinations of plasmonic nanostructures and molecular “glues” or linkers are employed to obtain nanoassemblies, such as nanobranches and core–satellite morphologies. An advanced nanoassembly morphology comprising multiple linear tentacles anchored onto a spherical core is reported here. Importantly, this core‐multi‐tentacle‐nanoassembly (CMT) benefits from numerous plasmonic interactions between multiple 5 nm gold nanoparticles (NPs) forming each tentacle as well as tentacle to core (15 nm) coupling. This results in an intense LSPR across the “biological optical window” of 650−1100 nm. It is shown that the combined interactions are responsible for the broadband LSPR and the intense electric field, otherwise not achievable with core–satellite morphologies. Further the sub 80 nm CMTs boosted NIR‐surface‐enhanced Raman scattering (SERS), with detection of SERS labels at 47 × 10‐9 m, as well as lower toxicity to noncancerous cell lines (human fibroblast Wi38) than observed for cancerous cell lines (human breast cancer MCF7), presents itself as an attractive candidate for use as biomedical theranostics agents.

Diagnostic prospects and preclinical development of optical technologies using gold nanostructure contrast agents to boost endogenous tissue contrast

“…Many different gold nanostructures are now available commercially, conrming the scalability of reproducible production. The ease of surface modication by functionalization with tags, 14,26,71,91 silica, 15 polymers, 92,93 DNA 67,94 or liposomes 95 has been a favourable factor for its use. Additionally, a coating of graphene oxide or silica onto gold nanostructures, 96,97 as well as incorporation of copper selenide (Cu-Se) into gold nanostructures 98,99 have been employed to boost the absorption cross-section and tune the LSPR into the NIR.…”

“…Such core-satellite morphologies have been reported using branched polymeric linkers with spherical core, 103 with DNA linkers utilizing gold nanorods as the core, 72,104 as well as with more complicated structures of caged gold nanorods as core. 105 Recently, Dey et al 91 have reported a distinct morphology of core multi-tentacle assemblies that provides the unique features of both core-satellites and branched nanochains. Such nano-assemblies feature an intense broadband absorbance extending throughout NIR I and exhibit dramatically improved NIR absorbance than that of core-satellite nanoassemblies.…”

Gold Nanorod Assemblies: The Roles of Hot-Spot Positioning and Anisotropy in Plasmon Coupling and SERS

“…Plasmonic nanostructures featuring control over their morphology and tunable optical properties, especially tunable localized surface plasmon resonance (LSPR) and surface-enhanced Raman scattering (SERS), are of interest to nanomaterial scientists [1][2][3][4]. The coupled LSPR mode appears when plasmonic nanoparticles (NPs) are close to each other, resulting in coupling of the individual plasmon oscillations via near-field interactions [5]. This coupling strongly impacts the electric field distribution around the nanostructure, especially at the NP-NP junctions, or "hot-spots".…”

“…In this regard, fabrication of various plasmonic nanoassemblies has been attempted. Among them, core-satellite nanoassemblies [5,17] have a unique arrangement, providing significantly better hot-spot control than other assemblies, such as globular assemblies, nanochains, and nanobranches [18,19]. Linker molecules that mediate the formation of such nanoassemblies and control the hot-spots (density and position) are, thus, significant.…”

Engineering Gadolinium‐Integrated Tellurium Nanorods for Theory‐Oriented Photonic Hyperthermia in the NIR‐II Biowindow

“…[7][8][9][10] Noteworthy, photo-driven heat conversion nanomaterials are indispensable for photonic hyperthermia, which could convert the near-infrared (NIR) light energy to generate regional heat for inducing tumor apoptosis. [11][12][13][14] However, recent progress of photonic hyperthermia mainly focuses on the first near-infrared light (NIR-I, 750-1000 nm) biowindow. [15][16][17][18] Comparatively, the second NIR biowindow (NIR-II, 1000-1700 nm) exhibits intrinsic advantages including minimal laser scattering coefficient, low photon absorbance, deep tissue penetration, and high maximum permissible exposure (MPE).…”