Triplex Au–Ag–C Core–Shell Nanoparticles as a Novel Raman Label

Abstract

Monodispersed, readily‐grafted, and biocompatible surface‐enhanced Raman spectroscopic (SERS) tagging materials are developed; they are composed of bimetallic Au@Ag nanoparticles (NPs) for optical enhancement, a reporter molecule for spectroscopic signature, and a carbon shell for protection and bioconjugation. A controllable and convenient hydrothermal synthetic route is presented to synthesize the layer‐by‐layer triplex Au–Ag–C core–shell NPs, which can incorporate the Raman‐active label 4‐mercapto benzoic acid (4‐MBA). The obtained gold seed–silver coated particles can be coated further with a thickness‐controlled carbon shell to form colloidal carbon‐encapsulated Aucore/Agshell spheres with a monodisperse size distribution. Furthermore, these SERS‐active spheres demonstrated interesting properties as a novel Raman tag for quantitative immunoassays. The results suggest such SERS tags can be used for multiplex and ultrasensitive detection of biomolecules as well as nontoxic, in vivo molecular imaging of animal or plant tissues.

SERS labels for quantitative assays: application to the quantification of gold nanoparticles uptaken by macrophage cells

“…The underestimation of the amount of SERS labels could be explained with the slow release of Raman reporters from the surface of AuNP in physiological medium, and can be avoided using more robust SERS labels like, for instance, labels obtained with thiolated dyes that are chemically bound to AuNP surface and/or encapsulating AuNP in silica shells. 18,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] These results confirmed that the method for the quantification of SERS labels based on UV-visible spectroscopy is reliable for biological applications in physiological medium. This new analytical approach required both small volumes (less than 20 ml) and small amounts of tissues per cells (about 25 000).…”

“…[4][5][6] Several bright examples about the application of SERS labels in nanobiotechnology and nanomedicine have been reported in recent years and various SERS labels have been developed. 18,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] For instance, gold nanoparticles capped with thiol terminated oligonucleotides composed of a Raman active molecule on the inner end and a DNA capture sequence have been used for the multiplexed detection of femtomolar amounts of more than six different DNA sequences in the same microarray. 20 In an analogous microarray set up, gold nanoparticles (AuNPs) with a targeting protein allowed the ultrasensible detection of proteins.…”

SERS Tags: Novel Optical Nanoprobes for Bioanalysis

“…93,118,153 Wang and colleagues used goat anti-hIgG and hIgG as a model system for protein detection. 118 A substrate coated with goat anti-hIgG was exposed to a solution containing different concentrations of hIgG.…”

Surface‐enhanced Raman spectroscopy in living plant using triplex AuAgC core–shell nanoparticles

“…[8] Currently, the principal approach of SERS tags is to use the SERS-active adsorbate as a reporter, and then encapsulate the particle(s) in polymer [9,10] or glass, [11,12] while more biocompatible carbon shells have also been demonstrated in our group recently. [13] Compared to the synthesis of polymeror silica-encapsulated SERS tags, this approach is a facile and absolutely 'green' method based on the carbonization of sugars, such as glucose, which involves no organic solvents, initiators, or surfactants. This ensures that the as-prepared SERS tags are nontoxic, enabling their use for in vivo detection.…”