title: Nanogold catalysis-based immunoresonance-scattering spectral assay for trace complement component 3.
abstract: 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 Na(2)HPO(4)-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 (HAuCl(4)-NH(2)OH) 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 HAuCl(4) and NH(2)OH to form particles, which exhibit a maximum RS peak at 585 nm. The decrease in RS intensity, DeltaI(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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: 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. zljiang@mailbox.gxnu.edu.cn
authors.forename: Zhiliang
authors.initials: Z
authors.lastname: Jiang
authors.forename: Wenxing
authors.initials: W
authors.lastname: Huang
authors.forename: Jiangping
authors.initials: J
authors.lastname: Li
authors.forename: Mingshun
authors.initials: M
authors.lastname: Li
authors.forename: Aihui
authors.initials: A
authors.lastname: Liang
authors.forename: Shengsen
authors.initials: S
authors.lastname: Zhang
authors.forename: Bing
authors.initials: B
authors.lastname: Chen
mesh_terms: D000906:Antibodies / Q000737:chemistry; D002384:Catalysis; D002712:Chlorides / Q000737:chemistry; D003176:Complement C3 / Q000032:analysis* / Q000276:immunology; D006046:Gold; D017612:Gold Compounds / Q000737:chemistry; D006801:Humans; D019811:Hydroxylamine / Q000737:chemistry; D007118:Immunoassay / Q000379:methods; D008027:Light; D053768:Metal Nanoparticles; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D009391:Nephelometry and Turbidimetry; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D013053:Spectrophotometry
chemical_list: D000906:Antibodies; D002712:Chlorides; D003176:Complement C3; D017612:Gold Compounds; D019811:Hydroxylamine; D006046:Gold; C024568:gold tetrachloride, acid