Catalytic Effect of Nanogold on Cu(II)−N₂H₄ Reaction and Its Application to Resonance Scattering Immunoassay

Abstract

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.

A highly sensitive resonance scattering spectral assay for carcinoembryonic antigen using immunonanogold as probe and nanocatalyst of NH2OH–Cu(II) particle reaction

“…CEA 1 mg/mL, and 1 mg/mL CEA antibody (CEAAb) (Bosai Biotechnology Limited Company, Zhengzhou, China) were prepared. The 10-nm nanogolds (19.3 lg/mL Au) were prepared with tri-sodium citrate according to reference [7]. The immunogold probe was prepared as follows: a 1.50-mL 0.1 mol/L K 2 CO 3 solution was added to a 100-mL nanogold solution to adjust the pH to about 6.5.…”

“…The RS effect of nanogold was combined with immunogold-labeled technology to enhance the selectivity, and some selective immunonanogold RS assays were established [4][5][6]. To further raise the sensitivity of the RS, some immunonanogold catalytic reactions were utilized, and the immunonanogold catalytic-gold (silver) particle techniques were proposed [7,8], with high sensitivity and selectivity. However, both the nanocatalytic reactions cannot be stopped easily.…”

A New and Sensitive Catalytic Resonance Scattering Spectral Assay for the Detection of Laccase Activity Using H2O2-I−-TDMAC System

“…[15][16][17][18][19][20] Recently, some immunoreaction, nanogold labeled immunoreaction and immunonanogold catalytic reaction have been utilized to establish some new RS methods for detection of antigen and haptene. [21][22][23][24] In addition, the combining RS technique with inorganic catalytic reaction and enzyme catalytic reaction was applied to analysis of trace inorganic ion, organic compound and enzyme activity. For example, using the enzyme catalytic effect, an enzyme catalytic-RS method for lysozyme activity was established.…”

Highly selective resonance scattering detection of trace thrombin using aptamer-modified AuRe nanoprobe

“…Compared with enzyme, nanogolds are more stable, easier to obtain, and are easily functionalized by antibody, aptamer. Recently, combined nanogold-catalytic reaction with RS effect of nanoparticle, some highly immunonanogold-catalytic [27,28] and aptamer-nanogold-catalytic RS analytical techniques [29] have been established. However, gold price is precious and the nanogold catalytic reaction is not plenty; thus it is necessary to prepare and utilize the gold composite nanoparticle, and to explore non-precious metal nanocatalytic reaction.…”