Robust Encapsulation of Biocompatible Gold Nanosphere Assemblies for Bioimaging via Surface Enhanced Raman Scattering

Abstract

femtomolar range in the context of surface-enhanced Raman scattering (SERS) spectroscopy. [9][10][11] In addition to high sensitivity, SERS nanoparticle substrates offer high photostability, multiplexing capability, narrow peak widths, and detailed spectroscopic information about molecules adsorbed on the AuNP surface. [12][13][14][15] An essential requirement for in vivo and living cell bioimaging involves chemical and colloidal stability under bioimaging conditions. [16] Moreover, a sensitive SERS tag requires the incorporation of molecules with high Raman cross-sections, socalled Raman reporter molecules (RaRs), which exhibit strongly enhanced Raman scattering when located in close contact with plasmonic substrates with high electromagnetic (EM) near-fields upon suitable light irradiation.Spherical AuNPs, which can be produced by straightforward and scalable methods, [17,18] display localized surface plasmon resonances (LSPR) in the range of 500-600 nm, but comparatively low SERS enhancement factors in the preferred NIR spectral region for bio-applications. [19][20][21] However, when two or more plasmonic NPs are assembled and brought into close proximity, the LSPR red-shifts and local EM enhancement increases significantly at the junctions between NPs, which are known as "hot spots". [22][23][24][25] Integration of RaRs inside such hot Controlled assembly of gold nanoparticles (AuNPs) into clusters is a promising avenue for the development of sensitive bioimaging and diagnostic tools based on surface-enhanced Raman scattering (SERS). However, several challenges, such as biocompatibility or colloidal and structural stability in biological environments, remain before AuNPs can be used as a tool for in vivo bioimaging. A versatile strategy for the preparation of colloidally stable and biocompatible AuNP clusters (AuNPCs) is introduced with high SERS signals, which are used as SERS contrast bioimaging agents (SERS tags). By tuning the ligand ratio of Raman reporter molecules to stabilizing polymer on the surface of each AuNP, aggregation can be carefully controlled. The resulting AuNPCs exhibit redshifted surface plasmon resonances in the near-infrared (NIR) region, as well as distinct electromagnetic hotspots that give rise to SERS analytical enhancement factors above 10 4 , compared to non-clustered spherical AuNPs. Thanks to the protective polymer shell, high levels of cellular uptake with low cytotoxicity are observed, allowing 3D SERS mapping of cells with sufficiently high spatial resolution to detect AuNPCs within intracellular organelles.

Aqueous Cellulose Nanocrystal-Colloidal Au Inks for 2D Printed Photothermia

“…After the ligand exchange of citrate by PVP, the AuNP solution plasmonic peak underwent a red shift of 3 nm (to 522 nm), as a consequence of the refractive index change around the Au core. 39 Given the improved water stability of the PVP-coated AuNPs, after modification, these nanoparticles could be easily mixed in aqueous solutions without any further change. Thermogravimetric analysis in Figure S3 reveals a PVP concentration of 5.1 wt % in the AuNPs, where a thermodegradation event originating from PVP is seen in the 240−550 °C range.…”

“…Water-dispersed citrate-coated AuNPs presented a maximum absorption peak at 519 nm (Figure b) corresponding to the nanoparticle LSPR dipolar mode. After the ligand exchange of citrate by PVP, the AuNP solution plasmonic peak underwent a red shift of 3 nm (to 522 nm), as a consequence of the refractive index change around the Au core . Given the improved water stability of the PVP-coated AuNPs, after modification, these nanoparticles could be easily mixed in aqueous solutions without any further change.…”

Ultrafast Laser‐Induced Plasmonic Modulation of Optical Properties of Dielectrics at High Resolution

“…LSPR can be excited by electromagnetic waves directly incident on NPs without specially designed structures to satisfy the wave vector matching condition, enabling optical localization and enhanced light-matter interactions in arbitrarily dielectric environments field. [5][6][7] In particular, plasmonic metamaterials composed of NPs exhibit potentially significant advantages in tailoring optical responses. NP assemblies strongly interact with light via plasmon resonances, providing a viable route to achieve multidimensional manipulation of near-field properties (e.g., intensity, polarization, phase, and spectral properties) and hence customization of the far-field effects.…”

Synthesis and Raman Detection of 5-Amino-2-mercaptobenzimidazole Self-Assembled Monolayers in Nanoparticle-on-a-Mirror Plasmonic Cavity Driven by Dielectric Waveguides

“…These interfaces play a crucial role in shaping the functionality and performance of these devices, which has led to significant interest in different fields of research. Therefore, understanding and manipulating interfaces at the nanoscale hold the key to unlocking new possibilities in fields such as catalysis, sensing, electronics, and biotechnology . In this context, the functionalization of surfaces with tailored molecular layers has become a fundamental approach to control and optimize interface properties …”

“…Therefore, understanding and manipulating interfaces at the nanoscale hold the key to unlocking new possibilities in fields such as catalysis, 1 sensing, 2 electronics, 3 and biotechnology. 4 In this context, the functionalization of surfaces with tailored molecular layers has become a fundamental approach to control and optimize interface properties. 5 Within this framework, gold (Au) surfaces have garnered significant attention due to their unique chemical and physical properties.…”