Gold-labeled nanoparticle-based immunoresonance scattering spectral assay for trace apolipoprotein AI and apolipoprotein B

Abstract

Background: Apolipoprotein AI (ApoAI) and ApoB are risk indicators of cardiovascular disease. We describe the use of immunoresonance scattering to measure the ApoAI and ApoB in serum. Methods: We used a trisodium citrate method to prepare 9.0-nm gold nanoparticles labeled with goat anti-human ApoAI and ApoB antibodies. The immune reaction between gold-labeled antibodies and antigens took place in Na2HPO4-NaH2PO 4 buffer solution (pH 6.4 for ApoAI and pH 6.0 for ApoB) in the presence of 75 g/L polyethylene glycol (PEG). We used a transmission electron microscope to observe the shape of the gold nanoparticles. Results were compared with those obtained by immunoturbidimetric methods. Twenty-five human serum samples were assayed by the immunoresonance scattering assay preset with the data indicated and by an immunoturbidimetric assay. Results: The presence of PEG greatly enhanced the intensity of resonance-scattering peaks at 560 nm. The intensity (ΔI) was proportional to concentration at 0.00833-0.3333 mg/L ApoAI and 0.00197-0.1972 mg/L ApoB. The detection limits were 2.04 and 0.96 μg/L for ApoAI and ApoB, respectively. The results for human serum samples were in agreement with those obtained with an immunoturbidimetric method. Linear regression analysis revealed a correlation coefficient, slope, and intercept of 0.915, 0.966, and 68.53 mg/L, respectively, for ApoAI and 0.919, 0.996, and 15.46 mg/L for ApoB. Conclusion: This method showed high sensitivity and good selectivity for quantitative determination of ApoAI and ApoB in human serum, with satisfactory results. © 2006 American Association for Clinical Chemistry.