Resonance Rayleigh Scattering Determination of Trace Hemin Basing on Aptamer-Modified Nanogold Catalysis of HAuCl4-Vitamine C

Hemin aptamer was used to modify gold nanoparticles (AuNPs) to obtain a stable aptamer-nanogold probe (AussDNA). In the condition of pH 8.0 Tris-HCl buffer solution containing 50mmol/L NaCl, the substrate chain of AussDNA was cracked by hemin to produce a short single-stranded DNA(ssDNA) and then further combined with hemin to form a stable hemin-ssDNA conjugate. The AuNPs released from AussDNA would be aggregated in the condition of 50mmol/L NaCl and exhibited a strong resonance Rayleigh scattering (RRS) peak at 368nm. Under the selected conditions, the increased RRS intensity (ΔI368nm) was linear to hemin concentration in the range of 5-750nmol/L, with a detection limit of 66 pmol/L. This RRS method was applied to determination of residual hemin in serum samples, with satisfactory results. The remnant AussDNA in the solution exhibited a strong catalytic activity on the gold particle reaction of HAuCl4-vitamine C (VC) that can be monitored by RRS technique at 368 nm. When the hemin concentration increased, the AussDNA decreased, the catalysis decreased, and the RRS intensity at 368nm decreased. The decreased RRS intensity ΔI368nmwas linear to the hemin concentration in the range of 1-200nmol/L, with a detection limit of 54 pmol/L. Accordingly, a sensitivity, selectivity, and simplicity new method of resonance Rayleigh scattering spectra to detect hemin using aptamer-modified nanogold as catalyst was established.

Resonance Rayleigh Scattering Spectral Determination of Vitamin C by Nanogold Catalysis

The nanogold catalysis effect on the reaction between HAuCl4 and Vitamin C (VC) was studied by resonance Rayleigh scattering (RS) spectroscopy at 540 nm, and a simple, rapid RS spectral method was established to determine VC. Under the chosen conditions, the increased intensity at 540 nm was linear to the VC concentration in the range of 7×10-6-2.8×10-4mol/L, with a regression equation of ΔI540 = 2.98 CVC + 13.4, a correlation coefficient of 0.9909 and a detection limit of 2×10-6 mol/L VC. The proposed method was applied to detect VC content in VC tablets and beverage samples, with simplicity, rapidity and accuracy.

Nanogold Catalysis–Based Immunoresonance-Scattering Spectral Assay for Trace Complement Component 3

Background: Complement component 3 (C3) is an essential bridge linking innate immunity and adaptive immunity. We describe an immunonanogold catalytic resonance-scattering (RS) technique for assaying C3 in serum. Methods: We used nanogold to label goat antihuman C3 antibody to obtain an immunonanogold RS probe for C3. The immune reaction between nanogold-labeled antibodies and antigens was carried out in Na2HPO4–sodium citrate buffer, pH 5.6, containing polyethylene glycol. After centrifuging the particle suspension, we used RS to monitor the catalytic effect of nanogold-labeled anti-C3 in the supernatant on the chlorauric acid–hydroxylamine (HAuCl4–NH2OH) particle reaction and used electron microscopy to monitor particle shape. We assayed 36 human serum samples with the immunonanogold catalytic RS assay and immunoturbidimetry. Results: Nanogold-labeled anti-C3 had a marked catalytic effect on the reaction of HAuCl4 and NH2OH to form particles, which exhibit a maximum RS peak at 585 nm. The decrease in RS intensity, ΔIRS, of the nanocatalytic system was proportional to C3 concentration from 5.0 to 160.0 ng/L. The detection limit for the C3 assay was 1.52 ng/L. Results obtained with serum samples agreed with those obtained with an immunoturbidimetric method. A linear regression analysis of 28 nonpathologic serum samples revealed a correlation coefficient of 0.960, with mean (SD) slope and intercept values of 0.787 (0.0218) g/L and 0.28 (0.026) g/L C3, respectively. Conclusion: The immunonanogold catalytic RS assay showed high sensitivity and good selectivity for measuring C3 in human serum. This method may become useful for diagnosing certain diseases, such as hepatitis.