Single Gold Nanoparticles Counter: An Ultrasensitive Detection Platform for One-Step Homogeneous Immunoassays and DNA Hybridization Assays

Abstract

In this paper, we present for the first time a single gold nanoparticle counter (SGNPC) in solution based on the photon bursting in a highly focused laser beam (less than 1 fL) due to the plasmon resonance scattering and Brownian motion of gold nanoparticles (GNPs). The photon burst intensity of single 36 nm GNPs is several tens to hundreds times stronger than that of quantum dots (QDs) and organic dyes. The relationship between the photon burst counts and GNPs concentration shows an excellent linearity. The linear range is over 4 orders of magnitude, and the detection limit of GNPs (36 nm) is 17 fM. On the basis of this single nanoparticle technique, we developed an ultrasensitive and highly selective detection platform for homogeneous immunoassay and DNA hybridization assays using GNPs as probes, which were 2-5 orders of magnitude more sensitive than current homogeneous methods. We used this technology to construct homogeneous sandwich immunoassays for cancer biomarkers, such as carcinoembryonic antigen (CEA) and alpha fetal protein (AFP), and aptamer recognition for thrombin. The detection limits are 130 fM for CEA, 714 fM for AFP and 2.72 pM for thrombin. Our method was successfully applied for direct determination of CEA, AFP and thrombin levels in sera from healthy subjects and cancer patients. In homogeneous DNA hybridization detection, we chose methylenetetrahydrofolate reductase (MTHFR) gene as a target. This assay successfully distinguished DNA sequences with single base mismatches, and the detection limits for the target were at 1 fM level.

Ultrahighly Sensitive Homogeneous Detection of DNA and MicroRNA by Using Single‐Silver‐Nanoparticle Counting

“…SSNPC system: A schematic representation of the SSNPC system is shown in the Supporting Information (Figure S1); the system is similar to the (FCS) system [35] and the single-GNP counting system. [26] Its basic principle is based on the photon-burst counting of single Ag NPs in a highly focused laser beam due to Brownian motion and resonance Rayleigh scattering of single Ag NPs. As shown in Figure 1 a, when single Ag NPs diffuse into and out of the small illumination volume through Brownian motion, photon bursting will be generated, which can be monitored in real time by an avalanche photodiode.…”

“…by using GNPs as probes, and the detection limits were at the pm and fm levels. [26] In fact, the resonance Rayleigh scattering intensity of silver nanoparticles (Ag NPs) is much stronger than that of the same-size GNPs. [27][28][29] We reasoned that Ag NPs should be much better as probes than GNPs if the sensitivity of resonance Rayleigh scattering techniques is considered.…”

Ultrasensitive photoelectrochemical immunoassay through tag induced exciton trapping

“…The linear response range was wider than those based on fluorescence resonance energy transfer (0.8-45.0 μg/L) [29], time-resolved fluoroimmunoassay (0.1-100 μg/L) [30], near-infrared fluorescence immunoassay (1.9-51.9 ug/L) [31] and chemiluminescent immunoassay (0.1-5.0 μg/L or 1.0-120 μg/L) [32,33]. The LOD was also lower than those of fluorescence resonance energy transfer (0.41 μg/L) [29], time-resolved fluoroimmunoassay (0.1 μg/L) [30], chemiluminescent immunoassay (0.01 μg/L, 0.16 μg/L) [32,33], fluorescence quenching (11.7 μg/L) [34], laser-induced fluorescence (1 μg/L) [35] and gold nanoparticles based immunoassay (49.3 μg/L) [36], showing better analytical performance. The wide linear range and low LOD extended the practical application of the proposed method.…”

Preparation and analysis of the Au-SiO2 multi-layer nanospheres as high SERS resolution substrate

“…The longitudinal plasmon band is extremely sensitive to changes in the dielectric properties in the surroundings, leading to strong, characteristic absorption bands in the visible to infrared part of the spectrum 1,2 A significant change in the plasmon spectra in response to the change in the refractive index in the vicinity of the gold nanorods arises from the localized surface plas-mon resonance (LSPR) properties and can be effectively utilized to detect specific target binding events. Recently, LSPR has been applied to the detection of DNA and other biomolecules using an analyte-induced aggregation/assembly of gold nanospheres 3,4 . Multi-layer nanocomposite material overweighs single material particle in many aspects, such as higher stability, stronger absorption spectrum, red-shift effect and so on.…”