Surface plasmon resonance: signal amplification using colloidal gold nanoparticles for enhanced sensitivity

Abstract

Among all the detection methods developed for bioassays, optical-based approaches are the most popular techniques. A widely used and accepted bioanalytical technique for routine characterization of molecular recognition events at a solid interface is surface plasmon resonance (SPR) spectroscopy. Compared with other techniques, SPR offers a series of advantages including rapid and real-time analysis, in situ detection, and the possibility to determine kinetic as well as thermodynamic parameters of interacting partners without the requirement of tagging one of the two partners. This method is nowadays used in academic and industrial research laboratories for drug discovery processes, safety, and quality control applications as well as for understanding bioaffinity reactions. Past studies have shown that SPR can detect approximately 100 ng/l of proteins. Currently, much effort is still invested to further improve SPR with respect to the sensitivity in the detection of low molecular weight analytes as well as in the detection limit for different analyte/ ligand reactions. This review will focus on the use of gold nanoparticles as an amplification strategy in SPR sensing. Compared to other review articles highlighting the several synthetic routes and properties of gold nanoparticles and research utilizing gold nanoparticles for various sensing strategies, this review will exclusively look at the impact of gold nanostructures for ultrasensitive SPR sensing. Signal enhancement by gold nanoparticles is caused by several effects such as surface mass increase due to enhanced surface area, larger refractive index changes by the particle mass, themselves, and electromagnetic field coupling between the plasmonic properties of the particles (localized surface plasmon resonance) and propagating plasmons. The unique optical, electronic, and catalytic properties of gold nanoparticles put them into the forefront of interest for signal amplification as will be outlined here.

Functionalized gold nanostructures: promising gene delivery vehicles in cancer treatment

“…139 RNA induces low response in SPR detection as it has lower mass, hence AuNPs are used to produce effective results for detection as it has high mass. 140,141 Western Blot and Nano Tracking Analysis (NTA) were the techniques used for AuNP@PEG@anti-RAB27A to evaluate the exosomes release. Consequence of it was the reduction of exosomes secretion and also exported the nanoparticles to recipient cells, hence decrease of the exosome release.…”

Functionalized Inorganic Nanoparticles for Magnetic Separation and SERS Detection of Water Pollutants

“…Colloidal Au and Ag NPs have been extensively employed as substrates for SERS , , . In both cases, the existence of LSPR causes strong absorption in the visible region, which explains their intense color, respectively red ( λ max at about 540 nm) and yellow ( λ max at about 420 nm), the exact location depending on factors such as local environment, shape and particle size distribution , . For instance, Figure shows the visible spectra of Au nanospheres and nanostars; the latter are anisotropic NPs that exhibit two surface plasmon resonance bands corresponding to the hybridization of plasmons localized at the core and tips .…”

Current achievements of nanoparticle applications in developing optical sensing and imaging techniques

“…According to Maxwell’s equations, the dispersion relation of surface plasmon waves can be derived with the boundary conditions determined from the interface of the metal and dielectric layers as described below: where ε metal and ε dielectric are the permittivity of the metal and dielectric layers, respectively, ω is the angular frequency of the incident light, and c is the speed of light. k SP is the surface momentum parallel to the interface between the metal and dielectric layers [ 46 ].…”