Received on May 10, 2007
Accepted on October 16, 2007

Automation and Analytical Techniques

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

¹ Key Laboratory of New Processing Technology for Nonferrous Metals and Materials of Education Ministry, Department of Material and Chemical Engineering, Guilin University of Technology, Guilin, China and, School of Environment and Resource, Guangxi Normal University, Guilin, China
² School of Environment and Resource, Guangxi Normal University, Guilin, China
³ Key Laboratory of New Processing Technology for Nonferrous Metals and Materials of Education Ministry, Department of Material and Chemical Engineering, Guilin University of Technology, Guilin, China

^* To whom correspondence should be addressed. E-mail: zljiang{at}mailbox.gxnu.edu.cn or zljiang@glite.edu.cn.

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, I_RS, 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.