Aihui Liang

Resonance Scattering Spectral Detection of Trace Hg2+ Using Aptamer-Modified Nanogold as Probe and Nanocatalyst

Single-strand DNA (ssDNA) was used to modify 10 nm nanogold to obtain an aptamer-modified nanogold resonance scattering (RS) probe (AussDNA) for detection of Hg(2+). In the presence of NaCl, Hg(2+) interacts with AussDNA to form very stable double-strand T-Hg(2+)-T mismatches and release nanogold particles that aggregate to large nanogold clusters causing the RS intensity at 540 nm to be enhanced linearly. On those grounds, 1.3-1667 nM Hg(2+) can be detected rapidly by the aptamer-modified nanogold RS assay, with a detection limit of 0.7 nM Hg(2+). If the large nanogold clusters were removed by membrane filtration, the excess AussDNA in the filtrate solution exhibits a catalytic effect on the new Cu(2)O particle reaction between NH(2)OH and Cu(2+)-EDTA complex at 60 degrees C. The excess AussDNA decreased with the addition of Hg(2+), which led the Cu(2)O particle RS intensity at 602 nm to decrease. The decreased RS intensity (DeltaI(602nm)) had a linear response to Hg(2+) concentration in the range of 0.1-400 nM, with a detection limit of 0.03 nM Hg(2+). This aptamer-modified nanogold catalytic RS method was applied for the detection of Hg(2+) in water samples, with sensitivity, selectivity, and simplicity.

Catalytic effect of nanogold on Cu(II)-N2H4 reaction and its application to resonance scattering immunoassay.

In the medium of EDTA-NaOH, nanogold strongly catalyzed the slow reaction between hydrazine (N2H4) and Cu(II) to form Cu particles, which exhibited a strong resonance scattering (RS) peak at 602 nm. The increased RS intensity at 602 nm (DeltaI(RS)) was linear to the nanogold concentration in the range of 0.008-2.64 nM, with a detection limit of 1.0 pM Au. The rate equation obtained by the initial rate procedure was V(Cu) = K(Cu)[C(Cu(II))](2)C(OH)(1)C(Au)(1)C(N2)H4(1), with an apparent activation energy of 38 kJ x mol(-1), and the catalytic reaction mechanism was also discussed. An immunonanogold-catalytic resonance scattering spectral (RSS) assay was established for detection of microalbumin (Malb), using 10 nm nanogold to label goat antihuman Malb to obtain an immunonanogold probe (AuMalb) for Malb. In pH 5.0 citric acid-Na2HPO4 buffer solution, the AuMalb aggregated nonspecifically. Upon addition of Malb, it reacted with the probe to form dispersive AuMalb-Malb immunocomplex in the solution. After centrifugation, the supernatant containing AuMalb-Malb was obtained, and exhibited a catalytic effect on the reaction of N2H4-Cu(II) to produce large Cu particles that resulted in the I(602 nm) increasing. The increased RS intensity at 602 nm (DeltaI(602 nm)) was linear to Malb concentration (C(Malb)) in the range of 0.4 to 460 pg x mL(-1), with the regression equation of DeltaI(602 nm) = 0.3713 C(Malb) + 7.2, correlation coefficient of 0.9981 and detection limit of 0.1 pg x mL(-1) Malb. The proposed method was applied to detect Malb in healthy human urine samples, with satisfactory results.

Resonance scattering spectral detection of trace ATP based on label-free aptamer reaction and nanogold catalysis

Double-stranded DNA (dsDNA) cannot protect gold nanoparticles (AuNPs) in the presence of NaCl, and dsDNA interacted with adenosine triphosphate (ATP) to form stable G-quartet and a single-stranded DNA (DNA 2) that can protect AuNPs. The unprotected AuNPs were aggregated to AuNP aggregations (AuNPA) that exhibited a resonance scattering (RS) peak at 590 nm. The RS intensity at 590 nm decreased linearly when the ATP concentration increased in the range of 6.6-110 nM. The catalysis of AuNP-DNA 2 was stronger than that of the AuNPA on the glucose-Cu(II) particle reaction, and the product appeared as an RS peak at 620 nm. When the ATP concentration was increased, the AuNP-DNA 2 increased, and the RS intensity at 620 nm increased linearly. The increased RS intensity (ΔI(620 nm)) was linear to ATP concentration in the range of 2.2-220 nM, with a regression equation of ΔI(620 nm) = 0.709C + 7.7, and a detection limit of 0.5 nM. Hereby, a new RS method of ATP detection was set up with high sensitivity and selectivity.

A highly selective nanogold-aptamer catalytic resonance scattering spectral assay for trace Hg2+ using HAuCl4-ascorbic acid as indicator reaction

Single strand DNA (ssDNA) was used to modify nanogold to obtain a nanogold-aptamer resonance scattering (RS) probe (NGssDNA) for Hg(2+), based on the formation of stable thymine-Hg(2+)-thymine (T-Hg(2+)-T) mismatches and aggregation of the released nanogold particles. After removing the aggregated particles by filtrate membrane, the excess NGssDNA in the filtration solution exhibit catalytic effect on the gold particle reaction between HAuCl(4) and ascorbic acid (AA) that appear as RS peak at 596nm. When Hg(2+) concentration increased, the RS intensity at 596nm decreased. The decreased intensity is linear to Hg(2+) concentration in the range of 0.00008-0.888ng/mL Hg(2+), with detection limit of 0.000034ng/mL. The nanogold-aptamer catalytic RS assay was applied to determination of Hg(2+) in water with satisfactory results.

Functional Nucleic Acid Nanoparticle-Based Resonance Scattering Spectral Probe

Highly sensitive and selective resonance Rayleigh scattering (RRS) and surface enhanced resonance Raman scattering (SERRS) spectral detection technique are developed by combining the functional nucleic acid including aptamer and DNAzyme, and nanoparticle such as gold/silver (NG/NS) aggregation and catalysis reaction. The recent progress of resonance scattering spectral technologies including RRS and SERRS are reviewed in this paper.

Catalysis of aptamer-modified AuPd nanoalloy probe and its application to resonance scattering detection of trace UO22+

AuPd nanoalloy and nanopalladium with a diameter of 5 nm were prepared, using sodium citrate as the stabilizing agent and NaBH(4) as the reductant. The nanocatalyst containing palladium on the surface exhibited a strong catalytic effect on the slow NiP particle reaction between NiCl(2) and NaH(2)PO(2), and the NiP particle system showed a resonance scattering (RS) peak at 508 nm. The RS results showed that the Pd atom on AuPd nanoalloy surface is the catalytic center. Combining the aptamer cracking reaction of double-stranded DNA (dsDNA)-UO(2)(2+), AuPd nanoalloy aggregation, and AuPd nanoalloy catalysis, both AuPd nanoalloy RS probe and AuPd nanoalloy catalytic RS assays were developed for the determination of 40-250 pmol L(-1) UO(2)(2+) and 5.0-50 pmol L(-1) UO(2)(2+), respectively.

A stable and reproducible nanosilver-aggregation-4-mercaptopyridine surface-enhanced Raman scattering probe for rapid determination of trace Hg2+

A stable nanosilver solution was prepared, using PEG10000 as stabilizer and NaBH(4) as reducer. In pH 6.6 Na(2)HPO(4)-NaH(2)PO(4) buffer solution containing PEG10000 and NaCl, the nanosilvers (AgNPs) were aggregated to form the stable nanosilver-aggregation (AgNPA) that could conjugate with 4-mercaptopyridine (MPy) to obtain an AgNPA-MPy surface-enhanced Raman scattering (SERS) probe with a strong SERS peak at 1097 cm(-1). When Hg(2+) concentration increased, the SERS intensity at 1097 cm(-1) decreased linearly as the stable complex of [Hg(MPy)(2)](2+) was formed and the AgNPA particles precipitate to the bottom. The decreased SERS intensity was linear to Hg(2+) concentration in the range of 50-3000 nmol/L. Based on this, a new sensitive SERS method has been proposed for the determination of trace Hg(2+) in the water sample, with satisfactory results.

SERS Detection of Dopamine Using Label-Free Acridine Red as Molecular Probe in Reduced Graphene Oxide/Silver Nanotriangle Sol Substrate

The reduced graphene oxide/silver nanotriangle (rGO/AgNT) composite sol was prepared by the reduction of silver ions with sodium borohydride in the presence of H2O2 and sodium citrate. In the nanosol substrate, the molecular probe of acridine red (AR) exhibited a weak surface-enhanced Raman scattering (SERS) peak at 1506 cm−1 due to its interaction with the rGO of rGO/AgNT. Upon addition of dopamine (DA), the competitive adsorption between DA and AR with the rGO took place, and the AR molecules were adsorbed on the AgNT aggregates with a strong SERS peak at 1506 cm−1 that caused the SERS peak increase. The increased SERS intensity is linear to the DA concentration in the range of 2.5–500 μmol/L. This new analytical system was investigated by SERS, fluorescence, absorption, transmission electron microscope (TEM), and scanning electron microscope (SEM) techniques, and a SERS quantitative analysis method for DA was established, using AR as a label-free molecular probe.

A novel nanocatalytic SERS detection of trace human chorionic gonadotropin using labeled-free Vitoria blue 4R as molecular probe

In pH 7.4 Na2HPO4-NaH2PO4 buffer solution containing the peptide probes for human chorionic gonadotropin (hCG), silver nanoparticles (AgNPs) were aggregated to big AgNPs clusters that exhibited very weak catalytic effect on the gold nanoparticle reaction of H2O2-HAuCl4. When hCG was present in the peptide probe solution, the AgNPs did not aggregate and it had strong catalytic effect on the gold nanoparticle reaction with a strong resonance Rayleigh scattering (RRS) peak at 370nm and a strong surface enhanced Raman scattering (SERS) peak at 1615cm(-1) in the presence of molecular probe of Victoria blue 4R (VB4R). With the increase of the hCG concentration, the catalysis enhanced due to the nanocatalyst of AgNPs increasing, and the RRS intensity increased at 370nm. The increased RRS intensity was linear to the hCG concentration in 0.05-10ng/mL, with a linear regression equation of ΔI370nm=409.8C +294. And the SERS intensity at 1615cm(-1) increased linearly with the hCG concentration in the range of 0.05-20ng/mL, with a linear regression equation of ΔI1615cm-1=142C+134. Based on this, two new methods of nanocatalytic SERS and RRS were proposed for the determination of trace hCG.

A highly sensitive resonance Rayleigh scattering assay for detection of Hg(II) using immunonanogold as probe

The monoclonal antibody (mAb) against Hg2+ was produced by the hybridoma technique, and was labeled using nanogold (NG) to obtain an immunonanogold (ING) probe. The immunoreaction takes place to form an ING–Hg2+ immunocomplex that caused the resonance Rayleigh scattering peak at 580 nm to decrease, with a detection limit of 1.1 nmol L−1 Hg2+.